Document process on how to enable/disable plugins with the opensearch_dashboards.yml config file

docs/plugins/config-yml-changes.md

@@ -0,0 +1,49 @@
+# Add new config to the {root}/config/opensearch-dashboards.yml file
+
+1. Add new config value in the opensearch_dashboards.yml file. Below is an example where I'm adding new flag to hide/show
+`wizard` plugin.
+
+```yml
+
+# Set the value of this setting to true to start exploring wizard
+# functionality in Visualization.
+# wizard.enabled: true
+```
+
+Note that the yml config values are read as path to the plugin config schema file. In the above example, `wizard` is the `Id` of the plugin to which I'm introducing this new config value.
+
+
+2. Create a new config schema for the plugin. We should have this config file defined in the root folder of the plugin. For example, `config.ts` for `wizard` plugin is defined in the `src/plugin/wizard/config.ts`
+
+```ts
+
+import { schema, TypeOf } from '@osd/config-schema';
+
+export const configSchema = schema.object({
+  enabled: schema.boolean({ defaultValue: true }),
+});
+
+export type ConfigSchema = TypeOf<typeof configSchema>;
+```
+Every plugin by default has `enabled` true if not defined in the config schema. When defined in the config schema, the value for if plugin should be enabled is read from here. This config value is overriden, when we define the config value in `opensearch_dashboards.yml`.
+
+3. Export the new config schema in the `index.ts` file of the plugin's server folder. This is required for plugin to read the properties to expose to client during plugin registration. 
+
+```ts
+export const config: PluginConfigDescriptor<ConfigSchema> = {
+  exposeToBrowser: {
+    enabled: true,
+  },
+  schema: configSchema,
+};
+
+```
+We need to set `exposeToBrowser` true for the config property `enabled` which we have defined in the config schema. 
+
+4. Now we can use the config schema in the `plugin.ts` class constructor, inside `public` folder of the plugin.
+
+```ts
+import { ConfigSchema } from '../config';
+
+constructor(public initializerContext PluginInitializerContext<ConfigSchema>) {}
+```