Enhance RPGLE syntax coloring

[chrjorgensen]

This PR will enhance the syntax coloring for RPGLE files:

• BIF's will be marked as support functions
• Compiler directives will be marked as keyword controls
• Operators will be marked as such
• Identifiers will be marked as variables

This PR was created since most syntax elements for RPGLE were keyword.other and produced a "dull" view of the code, in contrast to other languages in VS Code. With this PR more colors are used to identify elements in RPGLE code.

The RPGLE samples has also been updated with more syntax examples.

I have tested this but would like your 👀 on it as well.

[chrjorgensen]

@barrettotte If you think it is a good idea, I would be happy to step in as maintainer of this project next to you. I'm also maintainer for Code for IBM i and these two extensions are closely related.

This could be beneficial to all of us. Maybe @worksofliam would be interested as well - although I know he is very busy working for IBM and simultaneously on Code for IBM i and related extensions.

WDYT?

[barrettotte]

Awesome, colors and tweaks look good to me.

Haha wow yeah I should have added you and @worksofliam as contributors years ago. I apologize for waiting so long to do that; As of now, you both are contributors.

Unfortunately, my IBM i days may be over (outside of trying to restore an old AS/400). But, I can still be available for misc bug fixes if needed.

Thanks again for all the work you guys do.

[chrjorgensen]

@barrettotte Thank you for your trust and making me and @worksofliam contributors to this great extension.
And thank you for all your work so far - without you we would never have had this, and the IBM i community is so grateful!

Hopefully you will still be able to participate - your regexp knowledge is far superior to mine. If you need IBM i access, you can create an account on the free PUB400 IBM i.

Once again, thank you!