Update installation docs with `brew trust` command

[pavel-github]

Summary

On MacOS brew shows a warning message about untrusted hashicorp/taphashicorp/tap.

Warning: The following taps are not trusted:
  hashicorp/tap

Homebrew will ignore formulae, casks and commands from these taps when `HOMEBREW_REQUIRE_TAP_TRUST` is set.
This will become the default in Homebrew 6.0.0 or 5.2.0, whichever comes first.
Enable trust checks now with:
  export HOMEBREW_REQUIRE_TAP_TRUST=1
Trust specific formulae, casks or commands with:
  brew trust --formula <user>/<tap>/<formula>
  brew trust --cask <user>/<tap>/<cask>
  brew trust --command <user>/<tap>/<command>
or trust installed formulae from these taps with:
  brew trust --formula hashicorp/tap/packer hashicorp/tap/terraform
You can trust all formulae, casks and commands from these taps with:
  brew trust hashicorp/tap
Prefer trusting only the specific formulae, casks or commands you need.
Untap them with:
  brew untap hashicorp/tap
To keep allowing them by default during the transition:
  export HOMEBREW_NO_REQUIRE_TAP_TRUST=1
This is not recommended and will be removed in a later release.

Possible actions

Does it make sense to add brew trust hashicorp/tap command by all installation docs? Screenshot attached.

[hiSandog]

The installation docs should prefer the formula-specific brew trust --formula hashicorp/tap/<product> command rather than asking every user to trust the entire tap. That follows Homebrew's own least-privilege guidance in the warning and avoids silently extending trust to unrelated future formulae or commands. A shared docs partial generated with the product name would prevent Packer, Terraform, and other install pages from drifting.