Updates to CONTRIBUTING.md

[chrisdel101]

This task was noted as comments in various miscellaneous places, but wanted to make a note of the ongoing work.

Work will include:

• Expanding the document(s) overall word count to be more descriptive and give more information (and be more helpful).

• Giving specific beginner friendly examples of how to get started, i.e how to find files, how to get started.

• Giving specifics about what we expect in the code i.e. no prettifying, match style of current file's code, others?
  - Now we've started a bit of an informal style guide, it will good to communicate this to contributors before they commit.
  - Following issue Use a code formatter #1596, maybe we want to consider implementing an official code style guide? (@bjohansebas is doing, and has done, many things to improve alot of this). A discussion to be had another day...

• Telling contributor to open an issue and GET APPROVAL before making a PR.

• Tell them we expect both the description sections to be filled out, both for the Issue, and the PR.
  - I'm of the mind that we discard any submissions where these are left empty. Can I put this in? That we don't expect empty submissions?

• Inform about the ability to use the preview feature.

• Inform about the PR process (Submit issue-> Submit PR-> Review process-> Merge).

I was also thinking: We could add a contributions section promoting the expressJS documentation, expressjs.com, to the contributing HTML page on the website itself? Adding this could be a useful way to promote contributions and the standards we expect. Either we'd put it at the bottom of the current page, or add a new page somewhere.

This issue will only handle CONTRIBUTING.md for the repo.

[bjohansebas]

We could add a contributions section promoting the expressJS documentation, expressjs.com, to the contributing HTML page on the website itself? Adding this could be a useful way to promote contributions and the standards we expect. Either we'd put it at the bottom of the current page, or add a new page somewhere.

Could we add back the 'edit page' function in the footer, which was removed in #1548?

[bjohansebas]

It would be good to add that the API documentation does not need to be translated.