Update index.rst to include tip about enabling mavsdk-server debug output - #777

Unexpected input(s) 'tags', valid inputs are ['repository', 'ref', 'token', 'ssh-key', 'ssh-known-hosts', 'ssh-strict', 'ssh-user', 'persist-credentials', 'path', 'clean', 'filter', 'sparse-checkout', 'sparse-checkout-cone-mode', 'fetch-depth', 'fetch-tags', 'show-progress', 'lfs', 'submodules', 'set-safe-directory', 'github-server-url']