Align DEVELOPMENT.md with last release

[sestegra]

Since package.json file has been updated in previous release, the contribution documentation should be aligned with related updates.

[jpogran]

Thank you @sestegra for the help with the documentation! There are a couple of clarifying points here that you couldn't know about because we haven't circled back and updated things here.

I'll respond more inline, but in general we moved from updating each TextMate product JSON file individually to having YAML files with product specific information. This way we can build JSON with whatever overrides or specific rules needed, without having to maintain duplication across several files.

We chose to use Go to build out these files because it's closer to our toolchain in other parts of the company. I can understand if everyone does not want to install Go just to build the files, so I have it as a future task to add functionality here to help with that, but have not gotten to it yet.

If you don't mind, I'll add onto this PR with the steps needed as additional commits.

[sestegra]

Feel free to add your commits to this PR.

[radeksimko]

LGTM, I just left some comments in-line, although most of them are related to the original content that you just moved around.