Add a Team mkcert CA on vm-gitlab subsection to infra/README.md so
the dockerised dev mode scales to a multi-dev team: one shared CA
held on vm-gitlab, public rootCA.pem distributed to each developer's
Windows trust store, R&D Lead mints per-VM certs on vm-gitlab. The
CA private key never leaves vm-gitlab.
The solo flow already in the HTTPS dev-server setup section stays
the entry point for the first dev; this subsection picks up where
that one ends and answers the next question — how a teammate can
browse another dev's VM with a green padlock.
Covers initial CA setup on vm-gitlab, the canonical mkcert per-VM
mint command, onboarding a new dev (rootCA.pem + per-VM cert
delivery + Windows-side import), and operational notes (departures,
CA rotation, per-VM rotation, migration to a future corp-CA cert).
No code changed.
Julien Gautier