Enhance README with KDL patch guidelines

Added detailed documentation for KDL patches and editing policy.

Author: Bashamega

inputfiles/README.md

@@ -4,6 +4,62 @@ Some files in this directory are generated. Please do not edit them.
 This specifically includes:
 
 * `idl/*`
-* `mdn/*`
 
 Feel free to send a pull request with changes to any other files.
+Note It is recommended to add your patch use KDL format, continue reading to find out more.
+
+## Documentation for `patches/` KDL Folder
+
+The `patches/` directory only contains `.kdl` files that specify modifications ("patches") to the default Web IDL or related specifications, using the [KDL format](https://kdl.dev/).
+These modifications are integrated into the build system (see [`src/build/patches.ts`](../src/build/patches.ts) for implementation details).
+
+### Purpose
+
+- Fix errors or omissions in upstream IDL data.
+- Add or override interfaces, mixins, and enums.
+- Apply project-specific features or changes.
+
+### Editing Policy
+
+It is **recommended** to document and comment your patch files and their intent.
+This helps keep the integration clear and maintainable.
+
+### Structure & Parsing
+
+- All `.kdl` files in this folder are read and parsed at build time.
+- Their structure typically mirrors major Web IDL concepts:
+  - `enum`
+  - `interface`
+  - `interface-mixin`
+  - Members like `event`, `property`, and `method`.
+
+#### Example Patch File (`patches/my-patch.kdl`)
+```kdl
+// Add a readonly boolean property to Navigator
+interface "Navigator" {
+  property "experimentalField" type="boolean" optional=false
+}
+
+// Add a new value to an enum
+enum "MyEnum" {
+  ValueA
+  ValueB
+}
+```
+
+### How It Works
+
+The builder (see `src/build/patches.ts`):
+
+- Locates all KDL files in the `patches/` directory.
+- Parses and type-checks them.
+- Merges their contents and applies structural transformations over the main IDL dataset.
+
+See the source or comments in `patches.ts` for precise KDL syntax and advanced features.
+
+### Notes
+
+- You can split patches into multiple `.kdl` files if desired.
+- All the data in the json and jsonc files will be eventually transformed to KDL, so if possible submit patches to KDL.
+- When in doubt, consult `/src/build/patches.ts` for details on supported KDL structure and merging logic.
+- If there is a feature that is missing from the KDL parser, feel free to implement it yourself or ping @bashamega to help implement that feature in [this issue](https://github.com/microsoft/TypeScript-DOM-lib-generator/issues/2053), or just add it to the jsonc files.