Fix incorrect syntax highlighting for variables starting with "function"

[gowerc]

What problem did you solve?

Closes #982 - incorrect syntax highlighting for variables starting with the word function

• Resolved by adding a negative lookahead to the function-declarations file to make sure there are no additional word characters following the function keyword
• Added unit tests to show my code is working in the most basic settings
  • Unit tests work by reading in the regex pattern from the syntax file and then running them again pre-made strings.
  • Note that apparently vscode parses regex as POSIX but javascript doesn't so had to add a translation function.

Please let me know if there's a better way to test this or if you need me to refactor the code (am still learning node/ts/js/vscode).

(If you have)Screenshot

[gowerc]

Looks like the unit tests have failed with:

TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string. Received undefined

I'm assuming this is because the environment variable process.env.EXTENSION_ROOT isn't getting populated. I'm then guessing that this means the CICD job isn't using the same launch configuration as is being used by testing in vscode ?

[gowerc]

@renkun-ken , fixed the bug with pathing for getting the config file, this is ready for review now. Please let me know if there is a better way of handling this.

[renkun-ken]

LGTM thanks!