[eslint-plugin] update regex of matching TypeScript file extentions (Azure#32571)

Some of our custom rules perform operations on TypeScript files only and they use a regex of `/\.ts$/.test(fileName)` to check whether a file is TypeScript code file or not. With the migration to ESM, we can have *.mts and *.cts files as well. This PR updates the pattern to also match those files.

### Packages impacted by this PR
`@azure/eslint-plugin-azure-sdk`

Author: jeremymeng

common/tools/eslint-plugin-azure-sdk/src/rules/github-source-headers.ts

@@ -33,7 +33,7 @@ export default createRule({
   },
   defaultOptions: [],
   create(context) {
-    if (!/\.ts$/.test(context.filename)) {
+    if (!/\.ts|\.mts|\.cts$/.test(context.filename)) {
       return {};
     }
     return {

common/tools/eslint-plugin-azure-sdk/src/rules/ts-doc-internal.ts

@@ -113,7 +113,7 @@ export default createRule({
     const fileName = context.filename;
 
     // on the first run, if on a .ts file (program.getSourceFile is file-type dependent)
-    if (context.settings.exported === undefined && /\.ts$/.test(fileName)) {
+    if (context.settings.exported === undefined && /\.ts|\.mts|\.cts$/.test(fileName)) {
       const packageExports = getLocalExports(context);
       if (packageExports !== undefined) {
         context.settings.exported = packageExports;

common/tools/eslint-plugin-azure-sdk/tests/fixture/file-browser.mts

@@ -4,9 +4,11 @@
   },
   "include": [
     "file.ts",
+    "file-browser.mts",
     "package.json",
     "not_package.json",
     "src/test.ts",
+    "src/test-browser.mts",
     "tests/test.ts",
     "service-bus/package.json",
     "invalid/package.json",

common/tools/eslint-plugin-azure-sdk/tests/fixture/src/test-browser.mts

@@ -39,6 +39,11 @@ ruleTester.run("github-source-headers", rule, {
       code: valid,
       filename: "file.ts",
     },
+    {
+      // only the fields we care about
+      code: valid,
+      filename: "file-browser.mts",
+    },
     {
       // incorrect format but in a file we don't care about
       code: 'console.log("hello")',
@@ -57,6 +62,17 @@ ruleTester.run("github-source-headers", rule, {
       ],
       output: valid,
     },
+    {
+      // no comments .mts
+      code: 'console.log("hello")',
+      filename: "file-browser.mts",
+      errors: [
+        {
+          message: configError,
+        },
+      ],
+      output: valid,
+    },
     // wrong headers
     {
       code: invalid1,

common/tools/eslint-plugin-azure-sdk/tests/fixture/tsconfig.json

@@ -74,6 +74,15 @@ ruleTester.run("ts-doc-internal", rule, {
             function ExampleFunction() {}`,
       filename: "src/test.ts",
     },
+    {
+      code: `
+            /**
+             * Other documentation
+             * @hidden
+             */
+            function ExampleFunction() {}`,
+      filename: "src/test-browser.mts",
+    },
   ],
   invalid: [
     // class
@@ -119,5 +128,20 @@ ruleTester.run("ts-doc-internal", rule, {
         },
       ],
     },
+    // .mts file
+    {
+      code: `
+            /**
+             * Other documentation
+             * @ignore
+             */
+            function ExampleFunction() {}`,
+      filename: "src/test-browser.mts",
+      errors: [
+        {
+          message: "internal items with TSDoc comments should include an @internal or @hidden tag",
+        },
+      ],
+    },
   ],
 });