chore: update references to documentation
chore: update references to documentation

• https://docs.tocco.ch has been the canonical URL for some time.
• Replace badge as documentation is now built via GitLab CI. Rather
  than using the GitLab CI pipeline badge, I decided to go with a
  static badge. Using the GitLab CI badge, we'd end up with two
  badges labeled "pipeline" which would be more confusing than
  helpful.

tocco/tocco-client,tocco/tocco-client,tocco/tocco-client