Fix healthz socket

Forgot to resume. Went ahead and did the same for the test plugin
although it only sends messages and doesn't receive any.

release: v3.9.0

Unfortunately since plugins can now override the root this is necessary
or just can't log in.

Unfortunately we have existing plugins with routes there which we cannot
move.

docs: clarify Alpine install path in install.md

feat(testing): add unit tests for constants

docs(README.md): update to include requirements

feat(testing): add unit tests for src/common/http

Update README.md to include requirements

Promote ease of adoption by placing the requirements in the README at the root folder level.

This fixes the lint script but unfortunately breaks my editor.

Somehow I managed not to commit this earlier.

This can affect the test behavior and results.