Update to latest C# TextMate grammar

Add button to resource viewer to open unsupported resource in external program

Proposed Terminal API onData

**Bug**
Can't view cat gifs in VSCode resource viewer. We only display images that are < 1mb :(

**Fix**
Add a more specific error message for large images and adds button to try opening the file in an external program

* FrontMatter rendered properly on markdownEngine

* FrontMatter terminates for 3 - or .

* Regex applied on both files for markdown

* Send machineId in crash reports

* Update key for machineId to reflect that it was sent from vscode