Co-authored-by: Mike McQuaid <mike@mikemcquaid.com>

Co-authored-by: Issy Long <issyl0@github.com>

Why does Homebrew on Linux recommend that I install to
/home/linuxbrew/.linuxbrew?

Anywhere we can use `blob/master` we can use `blob/HEAD` instead. This
will make life easier if we ever rename our default branch in future
(once/if Git and GitHub provides the necessary tooling to do so).

I propose changing 'Why haven’t you pulled my pull request?' to 'Why haven’t you merged my pull request?' as, unless I'm missing a trick, this wording would fit more appropriately with what the question trying to ask?

This saves duplicating the (un)install instructions in multiple places.

- For some reason, the documented way of disabling a style for a
  specific section of Markdown text[1] didn't work for disabling the
  pronoun lint here. This is about the only place we have a legitimate
  need for it. Instead, sadly, squash this linting error by using his
  name.
- Also adjust the sentence for further clarity in light of this.

[1] - https://errata-ai.github.io/vale/config/#ignoring-parts-of-your-documents

- Move `odeprecated` to `odisabled`
- Remove `odisabled`
- Enable automatic cleanup on install/reinstall/upgrade.

Minor fix to improve readability.

Mostly edits to formatting, grammar, wording for consistency & readability.

I read through the docs locally and made various fixes.

Make some miscellaneous updates to stuff I noticed was wrong.

This reverts commit e63a2ee8.

Closes #3832.

Fixes #3021.

Add labeled fences to most code blocks, monospace terms where
appropriate, omit "$" when referring to variables

Also changes some heading levels so only one primary
heading appears per page.

Bare URLs are auto-linked on GitHub but not on docs.brew.sh, so I added
angle brackets around them where appropriate. Also converted
Markdown-linked URLs for clarity.

GitHub now nicely generates a documentation site for us at
http://brew.sh/brew based on our docs folder. Optimise the output of
this and the GitHub docs directory for readability and the various user
groupings.

Mostly related to the newer ways we’re handling versions and the
incoming deprecation of devel-only, head-only and versions.

After Issue #985 was merged, bottles for Mavericks are no longer
being built, meaning installations are triggering builds.

Update the FAQ to show that builds will most likely now be
triggers on Mavericks since their bottles are not being generated.

### Is there a glossary of terms around?
All your terminology needs can be [found here](docs/Formula-Cookbook.md#homebrew-terminology). results in 404 error

Addressing a few spots where I looked for terminology and did not find what I was looking for. Input based on a recent [podcast with Mike](https://changelog.com/podcast/223)

Closes #1040.