Set the explicitFileType of TypeScript files

TypeScript files are not correctly recognized by Xcode and *.ts files do
not display their contents. However, setting the explicitFileType key to
`sourcecode.javascript` forces Xcode to render the file correctly and enables file editing.

Change-Id: I3404a5d2e8423fad7e0d2ef832fc0d6476cb4b00
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/14000
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>

src/gn/xcode_object.cc

diff --git a/src/gn/xcode_object.cc b/src/gn/xcode_object.cc
index a957c97..c9b69a3 100644
--- a/src/gn/xcode_object.cc
+++ b/src/gn/xcode_object.cc
@@ -131,6 +131,7 @@
     {"storyboard", "file.storyboard"},
     {"strings", "text.plist.strings"},
     {"swift", "sourcecode.swift"},
+    {"ts", "sourcecode.javascript"},
     {"ttf", "file"},
     {"xcassets", "folder.assetcatalog"},
     {"xcconfig", "text.xcconfig"},
@@ -152,7 +153,7 @@
 }
 
 bool HasExplicitFileType(std::string_view ext) {
-  return ext == "dart";
+  return ext == "dart" || ext == "ts";
 }
 
 bool IsSourceFileForIndexing(std::string_view ext) {