Adds missing installation page and updates quick start

[froschdesign]

No description provided.

[froschdesign]

The DOCS_DEPLOY_KEY is the legacy key and must be replaced:

# check values
remote_repo=""
if [ -n "${DEPLOY_TOKEN}" ]; then
    remote_repo_setup remote_repo "${DEPLOY_TOKEN}"
else
    if [ -n "${DOCS_DEPLOY_KEY}" ]; then
        remote_repo_setup_legacy remote_repo "${DOCS_DEPLOY_KEY}"
    else
        print_error "Neither DEPLOY_TOKEN nor DOCS_DEPLOY_KEY found; please provide one or the other in your workflow env"
        kill -s KILL $TOP_PID
    fi
fi

https://github.com/laminas/documentation-theme/blob/c9c95a899460735dc06ccff05ec47d1c4f95e8ba/github-actions/docs/entrypoint.sh#L64-L75

[gsteel]

👍 LGTM!

[gsteel]

Test failures on latest here are fixed in 1.14.x in 3bb0704 - The failures concern changes to how PHPUnit deals with set_error_handler so it should be fine to release this patch - it'll go green when merged up to 1.14.x