fix: Clean up TeX syntax and add tests

1. Swap `\` for `\\` for TeX block comments to avoid issues with parsing
2. Add tests for TeX, Julia, AutoHotKey, Org mode, and Handlebars
3. Ensure tests can be run with 1 line command
4. Change logic in test framework so that tests run off of local version
   of `syntax.json` rather than remote version
5. Add details for running tests + adding tests for your syntax PR to
   readme
6. Add .gitignore file for python (to avoid compiles form tests winding
   up in commits)

syntax.json

@@ -408,8 +408,8 @@
       {
         "type": "block",
         "pattern": {
-          "start": "\\begin{comment}",
-          "end": "\\end{comment}"
+          "start": "\\\\begin{comment}",
+          "end": "\\\\end{comment}"
         }
       }
     ]