[BUG] Add missing keywords for syntax highlighting

[jimw567]

Describe the bug vs Expected Behaviour
As I develop more code in VSCode with the vsc-gsql-extension, I notice some keywords don't have the right highlighting. I will add them as I go. Below is the initial list:

INTERPRET QUERY

To Reproduce
Type the keywords above in VSC editor and check the highlighting

Screenshots
If applicable, add screenshots to help explain your problem.

Note the color difference between CREATE QUERY vs INTERPRET QUERY

VSCode Version: e.g. 0.0.2

Additional context
Add any other context about the problem here.

[jimw567]

@DavidBakerEffendi I can take care of the keywords issue as I go if that is ok with you. I will create a pull request once I am done. Just LMK.

[DavidBakerEffendi]

@jimw567 Thanks so much. Yeah, all the work is done under syntaxes/gsql.tmLanguage.json. Let me know if you get stuck and you can also shoot me messages on Discord under BigDataDave#9733.

[DavidBakerEffendi]

Something interesting to note and explain perhaps why it isn't highlighted, so I added everything from the EBNF and even on GraphStudio they don't highlight INTERPRET