[Monaco] Add support for gitignore files (#26331)

* [Monaco] Add support for gitignore files

* Update definition

* Fix

---------

Co-authored-by: Stefan Markovic <stefan@janeasystems.com>

src/common/FilePreviewCommon/FilePreviewCommon.csproj

@@ -20,6 +20,9 @@
     <None Update="customLanguages\reg.js">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>
+    <None Update="customLanguages\gitignore.js">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </None>
     <None Update="index.html">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>

src/common/FilePreviewCommon/customLanguages/gitignore.js

@@ -0,0 +1,13 @@
+export function gitignoreDefinition() {
+    return {
+        defaultToken: 'invalid',
+
+        tokenizer: {
+            root: [
+                [/^#.*$/, 'comment'],
+                [/^\s*!.*/, 'invalid'],
+                [/^\s*[^#]+/, "tag"]
+            ]
+        }
+    };
+}

src/common/FilePreviewCommon/monacoSpecialLanguages.js

@@ -1,6 +1,7 @@
 // This file adds new languages to monaco
 
 import { regDefinition } from './customLanguages/reg.js';
+import { gitignoreDefinition } from './customLanguages/gitignore.js';
 
 export async function registerAdditionalLanguages(monaco){
     await languageDefinitions();
@@ -13,6 +14,7 @@ export async function registerAdditionalLanguages(monaco){
     registerAdditionalLanguage("vbExt", [".vbs"], "vb", monaco)
     registerAdditionalLanguage("iniExt", [".inf", ".gitconfig", ".gitattributes", ".editorconfig"], "ini", monaco)
     registerAdditionalNewLanguage("reg", [".reg"], regDefinition(), monaco)
+    registerAdditionalNewLanguage("gitignore", [".gitignore"], gitignoreDefinition(), monaco)
 }
 
 // Language definitions taken from Monaco source code