Adds an alternative `Xcode` installation option for `macOS` and makes specifying the installation version easier.
Adds an alternative `Xcode` installation option for `macOS` and makes specifying the installation version easier.

General changes:
- Add documentation for installing with `xcode-select`, which takes up less disk space than `Xcode.app`
- Add `BAZEL_VERSION` environment variable to make these docs copy/paste-able.
  - Includes an example for installing the current latest version.

Changes related to `zsh` being the default shell on `macOS`:
- Add `shell` to code blocks without a language.
- Replace `bash` with `shell` on the rest of the code blocks.
- Add note about adding `PATH` to `.zshrc` along side `.bashrc`

PiperOrigin-RevId: 318100431

bazelbuild/bazel,safarmer/bazel,twitter-forks/bazel,davidzchen/bazel,katre/bazel,cushon/bazel,perezd/bazel,cushon/bazel,cushon/bazel,safarmer/bazel,perezd/bazel,ulfjack/bazel,katre/bazel,bazelbuild/bazel,twitter-forks/bazel,katre/bazel,twitter-forks/bazel,ulfjack/bazel,twitter-forks/bazel,perezd/bazel,davidzchen/bazel,perezd/bazel,bazelbuild/bazel,werkt/bazel,meteorcloudy/bazel,werkt/bazel,meteorcloudy/bazel,twitter-forks/bazel,werkt/bazel,ButterflyNetwork/bazel,ButterflyNetwork/bazel,safarmer/bazel,perezd/bazel,davidzchen/bazel,ulfjack/bazel,bazelbuild/bazel,cushon/bazel,davidzchen/bazel,ulfjack/bazel,ButterflyNetwork/bazel,safarmer/bazel,katre/bazel,ButterflyNetwork/bazel,bazelbuild/bazel,katre/bazel,perezd/bazel,ulfjack/bazel,ButterflyNetwork/bazel,meteorcloudy/bazel,ulfjack/bazel,meteorcloudy/bazel,meteorcloudy/bazel,werkt/bazel,meteorcloudy/bazel,safarmer/bazel,bazelbuild/bazel,cushon/bazel,meteorcloudy/bazel,werkt/bazel,ButterflyNetwork/bazel,cushon/bazel,katre/bazel,davidzchen/bazel,safarmer/bazel,davidzchen/bazel,ulfjack/bazel,twitter-forks/bazel,werkt/bazel,davidzchen/bazel,perezd/bazel,twitter-forks/bazel