Fix heading levels in specification.

specification/index.bs

@@ -11,33 +11,33 @@ Abstract: [Placeholder] Abstract.
 Markup Shorthands: markdown yes
 </pre>
 
-## File structure
+# File structure
 
 Once unpacked from the distribution format, a WebExtension is a directory containing a number of files.
 
 Note: In some operating systems, filenames are case insensitive. This can lead to naming collisions.
 
-### manifest.json
+## manifest.json
 
 A <a href="#manifest">Manifest</a> file.
 
-### _locales subdirectory
+## _locales subdirectory
 
 An optional directory containing strings as defined in <a href="#localization">localization</a>.
 
-### Other files
+## Other files
 
 An extension may also contain other files, such as those referenced in the <a href="#key-content_scripts">content_scripts</a> and <a href="#key-background">background</a> part of the <a href="#manifest">Manifest</a>.
 
-## Manifest
+# Manifest
 
 A WebExtension must have a manifest file at its root directory.
 
-### Manifest file
+## Manifest file
 
 A manifest file is a [[!JSON]] document named `manifest.json`. Malformed JSON files are not supported.
 
-### Manifest keys
+## Manifest keys
 
 If manifest keys that are not defined in this specification are specified, implementors must ignore those keys.
 
@@ -68,138 +68,138 @@ The following keys must be considered valid in Manifest V3:
 * <a href="#key-host_permissions">`host_permissions`</a>: optional
 * <a href="#key-optional_host_permissions">`optional_host_permissions`</a>: optional
 
-#### Key `manifest_version`
+### Key `manifest_version`
 
 This key must be present.
 
-#### Key `name`
+### Key `name`
 
 Name of the extension used in the browser’s user interface. This should be the full name used to identify the extension. See also <a href="#key-short_name">`short_name`</a>.
 
 This key must be present. This property can be localized.
 
-#### Key `version`
+### Key `version`
 
 This key must be present.
 
-#### Key `permissions`
+### Key `permissions`
 
 This key may be present.
 
-#### Key `optional_permissions`
+### Key `optional_permissions`
 
 This key may be present.
 
-#### Key `host_permissions`
+### Key `host_permissions`
 
 This key may be present.
 
-#### Key `optional_host_permissions`
+### Key `optional_host_permissions`
 
 This key may be present.
 
-#### Key `default_locale`
+### Key `default_locale`
 
 This key must be present if the `_locales` subdirectory is present, must be absent otherwise.
 
-#### Key `background`
+### Key `background`
 
 This key may be present.
 
-#### Key `commands`
+### Key `commands`
 
 This key may be present.
 
-#### Key `content_scripts`
+### Key `content_scripts`
 
 This key may be present.
 
-#### Key `content_security_policy`
+### Key `content_security_policy`
 
 This key may be present.
 
-#### Key `description`
+### Key `description`
 
 This key may be present.
 
-#### Key `icons`
+### Key `icons`
 
 This key may be present.
 
-#### Key `options_ui`
+### Key `options_ui`
 
 This key may be present.
 
-#### Key `short_name`
+### Key `short_name`
 
 The short name of the extension. This value should be used in contexts where <a href="#key-name">`name`</a> is too long to use in full. If `short_name` is not provided, manifest consumers should use a truncated version of `name`.
 
 This key may be present. This property can be localized.
 
-#### Key `web_accessible_resources`
+### Key `web_accessible_resources`
 
 This key may be present.
 
-#### Key `externally_connectable`
+### Key `externally_connectable`
 
 This key may be present.
 
-#### Key `devtools_page`
+### Key `devtools_page`
 
 This key may be present.
 
-### Reserved file names
+## Reserved file names
 
 Filenames beginning with an underscore (`_`) are reserved for use by user agent.
 
-## Isolated worlds
+# Isolated worlds
 
-## Unavailable APIs
+# Unavailable APIs
 
-## The `browser` global
+# The `browser` global
 
-## Extension origin
+# Extension origin
 
-## Localization
+# Localization
 
 The _locales subdirectory of a WebExtension can contain strings for internationalization purposes.
 
 Issue(62): Specify localization handling.
 
-## Host permissions
+# Host permissions
 
-### Cross-origin fetch
+## Cross-origin fetch
 
-## Match patterns
+# Match patterns
 
-## Concepts
+# Concepts
 
-### Uniqueness of extension IDs
+## Uniqueness of extension IDs
 
-### Promises and callbacks
+## Promises and callbacks
 
-### User gestures and activeTab
+## User gestures and activeTab
 
-### Extension permissions and web perissions
+## Extension permissions and web perissions
 
-## Content security policy
+# Content security policy
 
-## Architecture
+# Architecture
 
-### Background content
+## Background content
 
-### Content scripts
+## Content scripts
 
-#### Isolated worlds
+### Isolated worlds
 
-### Extension pages
+## Extension pages
 
-## Classes of security risk
+# Classes of security risk
 
-## Web accessible resources
+# Web accessible resources
 
-## Interaction with the web
+# Interaction with the web
 
-### Current behavior of cookie partitioning
+## Current behavior of cookie partitioning
 
-## Version number handling
+# Version number handling