message: Add discord badge
diff: <a href="https://app.codecov.io/gh/duckdb/duckdb">
  <img src="https://codecov.io/gh/duckdb/duckdb/branch/master/graph/badge.svg?token=FaxjcfFghN" alt="codecov"/>
  </a>
  + <a href="https://discord.gg/tcvwpjfnZx">
  + <img src="https://shields.io/discord/909674491309850675" alt="discord" />
  + </a>
  </p>
  ## DuckDB
  