DOC: better links in readme for newcomers

[tupui]

During the sprint, we noticed that almost every newcomers were looking into HACKING.rst.txt. This is confusing and we should have a single place for users to look at: our dev doc.

I propose to also move HACKING.rst.txt from the tree root into our doc. (not done yet here).

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Something else for the newcomers first path:

• At the end of the quick start guide, we should link to the dev workflow
• The dev workflow should be updated to use dev.py. This page is not very visible in the TOC (we can use bold or have it as text instead of in the list, add a link to it in the text at the top of the page, etc.).
• The dev workflow is somehow similar to the quick start document and they could almost be merged.

I can work on these in a PR if wanted.

@melissawm what do you think?

[mdhaber]

LGTM. I'll let @melissawm take a look (and maybe merge)?

[melissawm]

Looks good to me, just left a small suggestion to include a link to the devdocs here. Thanks @tupui

[tupui]

Thank you both for your review. I will merge this then.