This improves the load time of most brew commands. For an example of
one of the simplest commands this speeds up:
Without Bootsnap:
```
$ hyperfine 'git checkout master; brew help' 'git checkout optimise_requires; brew help'
Benchmark 1: git checkout master; brew help
Time (mean ± σ): 525.0 ms ± 35.8 ms [User: 229.9 ms, System: 113.1 ms]
Range (min … max): 465.3 ms … 576.6 ms 10 runs
Benchmark 2: git checkout optimise_requires; brew help
Time (mean ± σ): 383.3 ms ± 25.1 ms [User: 133.0 ms, System: 72.1 ms]
Range (min … max): 353.0 ms … 443.6 ms 10 runs
Summary
git checkout optimise_requires; brew help ran
1.37 ± 0.13 times faster than git checkout master; brew help
```
With Bootsnap:
```
$ hyperfine 'git checkout master; brew help' 'git checkout optimise_requires; brew help'
Benchmark 1: git checkout master; brew help
Time (mean ± σ): 386.0 ms ± 30.9 ms [User: 130.2 ms, System: 93.8 ms]
Range (min … max): 359.5 ms … 469.3 ms 10 runs
Benchmark 2: git checkout optimise_requires; brew help
Time (mean ± σ): 330.2 ms ± 32.4 ms [User: 93.4 ms, System: 73.0 ms]
Range (min … max): 302.9 ms … 413.9 ms 10 runs
Summary
git checkout optimise_requires; brew help ran
1.17 ± 0.15 times faster than git checkout master; brew help
```
Similarly to have we have with other commands, use Bash to speed it up.
Before:
```
$ hyperfine "brew list"
Benchmark 1: brew list
Time (mean ± σ): 559.9 ms ± 122.8 ms [User: 176.2 ms, System: 126.2 ms]
Range (min … max): 503.2 ms … 907.3 ms 10 runs
```
After:
```
$ hyperfine "brew list"
Benchmark 1: brew list
Time (mean ± σ): 223.7 ms ± 31.9 ms [User: 35.0 ms, System: 53.4 ms]
Range (min … max): 198.1 ms … 302.4 ms 10
```
Petty after comparison because someone on Homebrew/discussions compared
them:
```
$ hyperfine "brew list" "pip3 list"
Benchmark 1: brew list
Time (mean ± σ): 213.1 ms ± 22.8 ms [User: 34.2 ms, System: 49.2 ms]
Range (min … max): 191.2 ms … 272.3 ms 13 runs
Benchmark 2: pip3 list
Time (mean ± σ): 271.7 ms ± 4.6 ms [User: 191.9 ms, System: 40.0 ms]
Range (min … max): 264.7 ms … 281.4 ms 10 runs
Summary
brew list ran
1.28 ± 0.14 times faster than pip3 list
```
---
While we're here, also add the `HOMEBREW_CASKROOM` environment variable
to make things a bit cleaner and use `--caskroom` in documentation.
Co-authored-by: Carlo Cabrera <30379873+carlocab@users.noreply.github.com>
