INSTALL.md: Add FreeBSD

Update homebrew install link to point to homebrew website.

the git file in the homebrew repo does not provide a clear path to install

Fixes link for nixos package

v0.7.1

We don't have any particular reason to unset. Clearing should be good
enough, and avoid any errors using unset parameters.

Cherry-picked from PR #634

Always reset file descriptor after consuming it

Ensure that we're using the builtin exec

fix: Makefile SRC_DIR spacing

Cherry-picked from PR #706 and updates made to src/config.zsh.

Fixes issues #678

Create .gitignore for *.zwc

Install: Add Alpine Linux package

Update Install.md

Update INSTALL link for Mac OS - homebrew moved under z/

Update README.md

Clarify where to get `zpty` from.

Info from https://apple.stackexchange.com/a/416099 and https://zsh.sourceforge.io/releases.html .

The testing docker image has been split up. Instead of having one image
with all supported versions of zsh installed, we now have a separate
image for each supported zsh version.

We use GitHub Action matrices to run jobs in parallel for all of the
supported versions.

We no longer need to publish images to Docker Hub. The images are just
built by CI (or developers) as needed from the Dockerfile in the repo.

Adds steps to install zsh-autosuggestions via Homebrew Formulae.

This prevents the request cancelling logic from closing an unrelated fd that happens to reuse the same number.

v0.7.0

Disable ^C async workaround for zsh version 5.8 and later

Update INSTALL.md

[fix] install this plugin aside other plugins

Fixes/flaky ci

To reproduce:

1. Run `zsh -f`.
2. Run this:
  function bye() { BUFFER=bye }
  zle -N bye
  bindkey '^B' bye
  print -s 'hibye unexpected'
  source ~/zsh-autosuggestions/zsh-autosuggestions.zsh
3. Type `hi` and press Ctrl-B.

Expected: POSTBUFFER is empty.

Actual: POSTBUFFER is " unexpected".

There's something funny occasionally happening when `with_history` is
used twice in the same test. It seems to be happening more frequently
since asynchronous mode was enabled by default. My guess is it has
something to do with the `C-c` keys being sent toward the end not
consistently terminating the prompt. But I'm really not sure how it
would ever get into a `then` block like it seems to:

```
Failure/Error: wait_for { session.content }.to eq('echo "hello\nworld"')

  expected: "echo \"hello\\nworld\""
       got: "then> echo \"hello\\"
```

Sticking to only one `with_history` per terminal session (per test)
seems to fix the flakiness.

I also removed an old test case because I could not understand why it
was necessary and so couldn't write a good description for it. Could be
we'll need to add it back in at some point.

Write mock history to a temp file and load it directly with `fc -R`
instead of running each command individually to build up the history.

Enable async mode by default in newer versions of zsh

cleanup: Use more idiomatic method of checking if var is set

Be more specific about the built-in widgets we want to avoid wrapping