Improve typescript_tsdk lookup

Fix microsoft#538

This plugin is unusable without this change when dealing with Yarn PnP projects.

typescript/libs/editor_client.py

@@ -51,9 +51,16 @@ def initialize(self):
 
         # retrieve the path to tsserver.js
         # first see if user set the path to the file
-        settings = sublime.load_settings("Preferences.sublime-settings")
+        settings = sublime.active_window().active_view().settings()
         tsdk_location = settings.get("typescript_tsdk")
         if tsdk_location:
+            if not os.path.isabs(tsdk_location):
+                folders = sublime.active_window().folders()
+                if len(folders) == 0:
+                    raise ValueError("typescript_tsdk is set to a relative path \"" + tsdk_location + "\", but there are no folders open in the active window, so we don't know where to look for it")
+
+                tsdk_location = os.path.join(folders[0], tsdk_location)
+
             proc_file = os.path.join(tsdk_location, "tsserver.js")
             global_vars._tsc_path = os.path.join(tsdk_location, "tsc.js")
         else: