Support local `zilla` installation on MacOS via `homebrew`

[jfallows]

Describe the desired outcome from the user's perspective
As a MacOS developer, I want to be able to install zilla locally via homebrew.

Acceptance criteria

• brew install zilla works
• brew upgrade zilla works
• brew uninstall zilla works

Additional context
Decide homebrew formula vs cask packaging.
https://docs.brew.sh/How-to-Create-and-Maintain-a-Tap

Tasks

• Implement homebrew tap via GitHub repository aklivity/homebrew-tap
• Document how to install zilla via homebrew zilla-docs#223

[ankitk-me]

brew install zilla output:

% brew install zilla
==> Fetching adaemonthread/aklivity/zilla
==> Downloading https://raw.githubusercontent.com/aklivity/zilla/0.9.78/cloud/docker-image/src/main/docker/zpm.json.template
...
==> Installing zilla from adaemonthread/aklivity
==> wget https://maven.packages.aklivity.io/io/aklivity/zilla/manager/0.9.78/manager-0.9.78.jar
==> java -jar manager-0.9.78.jar wrap
==> ./zpmw install --debug
🍺  /opt/homebrew/Cellar/zilla/0.9.78: 11,480 files, 249.4MB, built in 5 minutes 3 seconds
==> Running `brew cleanup zilla`...
Disable this behaviour by setting HOMEBREW_NO_INSTALL_CLEANUP.
Hide these hints with HOMEBREW_NO_ENV_HINTS (see `man brew`).
Removing: /Users/ankit/Library/Caches/Homebrew/zilla--0.9.79.template... (2.2KB)

brew upgrade zilla output:

% brew upgrade zilla
==> Upgrading 1 outdated package:
adaemonthread/aklivity/zilla 0.9.78 -> 0.9.79
==> Fetching adaemonthread/aklivity/zilla
==> Downloading https://raw.githubusercontent.com/aklivity/zilla/0.9.79/cloud/docker-image/src/main/docker/zpm.json.template
...
==> Upgrading adaemonthread/aklivity/zilla
  0.9.78 -> 0.9.79
==> wget https://maven.packages.aklivity.io/io/aklivity/zilla/manager/0.9.79/manager-0.9.79.jar
==> java -jar manager-0.9.79.jar wrap
==> ./zpmw install --debug
🍺  /opt/homebrew/Cellar/zilla/0.9.79: 11,485 files, 250MB, built in 5 minutes 1 second
==> Running `brew cleanup zilla`...
Disable this behaviour by setting HOMEBREW_NO_INSTALL_CLEANUP.
Hide these hints with HOMEBREW_NO_ENV_HINTS (see `man brew`).
Removing: /opt/homebrew/Cellar/zilla/0.9.78... (11,480 files, 249.4MB)
Removing: /Users/ankit/Library/Caches/Homebrew/zilla--0.9.78.template... (2.1KB)

brew uninstall zilla output:

% brew uninstall zilla
Uninstalling /opt/homebrew/Cellar/zilla/0.9.79... (11,485 files, 250MB)