Add syntax highlighting for .env files without extensions (microsoft#155298)

Add syntax highlighting for .env files without extensions. Fixes microsoft#154111

Author: aeschli

extensions/ini/package.json

@@ -37,7 +37,8 @@
           ".editorconfig"
         ],
         "filenames": [
-          "gitconfig"
+          "gitconfig",
+          ".env"
         ],
         "filenamePatterns": [
           "**/.config/git/config",