Add README to the useSetting component (#53162)

* Add a README for the useSetting hook

* Tweak the readme to add more detail

packages/block-editor/src/components/use-setting/README.md

@@ -0,0 +1,39 @@
+## Use Setting
+
+`useSetting` is a hook that will retrive the setting for the block instance that's in use. 
+
+It does the lookup of the setting in the following order:
+
+1. Third parties can provide the settings for the block using the filter `blockEditor.useSetting.before`.
+2. If no third parties have provided this setting, then it looks up in the block instance hierachy starting from the current block and working its way upwards to its ancestors.
+3. If that doesn't prove to be successful in getting a value, then it falls back to the settings from the block editor store.
+4. If none of the above steps prove to be successful, then it's likely to be a deprecated setting and the deprecated setting is used instead.
+
+## Table of contents
+
+1. [Development guidelines](#development-guidelines)
+
+## Development guidelines
+
+### Usage
+
+This will fetch the default color palette based on the block instance.
+
+```jsx
+import { useSetting } from '@wordpress/block-editor';
+
+const defaultColorPalette = useSetting( 'color.palette.default' );
+```
+
+Refer [here](https://github.com/WordPress/gutenberg/blob/HEAD/docs/how-to-guides/curating-the-editor-experience.md?plain=1#L330) in order to understand how the filter mentioned above `blockEditor.useSetting.before` can be used.
+
+### Props
+
+This hooks accepts the following props.
+
+#### `path`
+
+-   **Type:** `String`
+-   **Default:** `undefined`
+
+The path to the setting that is to be used for a block. Ex: `typography.fontSizes`