Do not override existing index pages (#91)

* Don't override index.html pages with generated index pages

* Tidy index path logic

* Upgrade jest so it runs on latest version of Node 18

* Add note about index file generation to README

README.md

@@ -88,6 +88,14 @@ through because it is not markdown or asciidoc e.g. images
 
 ## Things to Consider
 
+### Index file generation
+
+Morty will automatically generate an `index.html` file for any directory that
+contains markdown or asciidoc files (or has descendants that contain these
+files). This file contains links to any documentation files or subdirectories
+the directory contains. The generation will be skipped for any directory that
+already contains an `index.md`, `index.asciidoc`, `index.adoc` or `index.asc` file.
+
 ### File & Directory Ordering
 
 These are sorted lexically (0-9 < a-z>).

jest.config.js

@@ -1,3 +1,6 @@
 module.exports = {
-  'snapshotSerializers': ['jest-serializer-html']
+  'snapshotSerializers': ['jest-serializer-html'],
+  'snapshotFormat': {
+    'printBasicPrototype': true
+  }
 }