Document Homebrew 6 tap trust requirement

[stagefright5]

Homebrew 6 introduced/enforced tap trust for non-official taps. Users with tap trust required now see warnings like:

Warning: Skipping redis/redis because it is not trusted. Run `brew trust redis/redis` to trust it.

Could the README / installation docs mention this for Homebrew 6 users? For example:

brew trust redis/redis

before installing/upgrading from this tap, if the user trusts it.

References:

• https://docs.brew.sh/Tap-Trust
• https://brew.sh/2026/06/11/homebrew-6.0.0/