Monorepo: added instructions on how to update report flaky tests action. (#50366)

.github/actions/report-flaky-tests/UPDATE.md

@@ -0,0 +1,78 @@
+# How to update
+
+## Source code
+
+This action is extracted and bundled version of the following:
+
+Repository: https://github.com/WordPress/gutenberg/tree/trunk/packages/report-flaky-tests
+Commit ID: ce803384250671d01fde6c7d6d2aa83075fcc726
+
+## How to build
+
+After checking out the repository, navigate to packages/report-flaky-tests and do some modifications:
+
+### package.json file
+
+Add the following dependency: `"ts-loader": "^9.5.1",`.
+
+### tsconfig.json file
+
+The file context should be updated to following state:
+
+```
+{
+	"$schema": "https://json.schemastore.org/tsconfig.json",
+	"extends": "../../tsconfig.base.json",
+	"compilerOptions": {
+		"outDir": "dist",
+		"target": "es6",
+		"module": "commonjs",
+		"esModuleInterop": true,
+		"moduleResolution": "node",
+		"declarationDir": "build-types",
+		"rootDir": "src",
+		"emitDeclarationOnly": false,
+	},
+	"include": [ "src/**/*" ],
+	"exclude": [ "src/__tests__/**/*", "src/__fixtures__/**/*" ]
+}
+```
+
+### webpack.config.js file
+
+The file should be added with the following content:
+
+```
+const path = require( 'path' );
+const buildMode = process.env.NODE_ENV || 'production';
+
+module.exports = {
+	entry: './src/index.ts',
+	target: 'node',
+	mode: buildMode,
+	module: {
+		rules: [
+			{
+				test: /\.tsx?$/,
+				use: 'ts-loader',
+				exclude: /node_modules/,
+			},
+		],
+	},
+	resolve: {
+		extensions: [ '.tsx', '.ts', '.js' ],
+	},
+	plugins: [],
+	output: {
+		filename: 'index.js',
+		path: path.resolve( __dirname, 'dist' ),
+		clean: true,
+	},
+};
+```
+
+### Build
+
+Run `webpack --config webpack.config.js` (don't forget about `npm install` before that).
+
+Use the generated files under `packages/report-flaky-tests/dist` to update the bundled distribution in this repository.