Should update to tree-sitter-markdown

[bennypowers]

Prerequisites

• Put an X between the brackets on this line if you have done all of the following:
  • Reproduced the problem in Safe Mode: https://flight-manual.atom.io/hacking-atom/sections/debugging/#using-safe-mode
  • Followed all applicable steps in the debugging guide: https://flight-manual.atom.io/hacking-atom/sections/debugging/
  • Checked the FAQs on the message board for common solutions: https://discuss.atom.io/c/faq
  • Checked that your issue isn't already filed: https://github.com/issues?utf8=✓&q=is%3Aissue+user%3Aatom
  • Checked that there is not already an Atom package that provides the described functionality: https://atom.io/packages

Description

language-gfm uses the old textmate grammar for markdown, which means it's using the oold grammars for embedded languages as well. language-gfm should use an up-to-date tree sitter grammar, e.g. tree-sitter-markdown

Steps to Reproduce

1. Use language-gfm
2. embedded grammars may not support up-to-date features, e.g. ?. ?? optional chaining and nullish coalescing in JavaScript

Expected behavior:

JavaScript with embedded html, itself embedded in markdown should render like:

Actual behavior:

Reproduces how often:

100%

Versions

atom --version

Atom : 1.58.0
Electron: 9.4.4
Chrome : 83.0.4103.122
Node : 12.14.1

apm 2.6.2
npm 6.14.13
node 12.14.1 x64
atom 1.58.0
python 2.7.16
git 2.28.0

Additional Information