Add TODOs badge to README (woodpecker-ci#731)

<a href="https://www.tickgit.com/browse?repo=github.com/woodpecker-ci/woodpecker" title="TODOs">
  <img src="https://badgen.net/https/api.tickgit.com/badgen/github.com/woodpecker-ci/woodpecker">
</a>

README.md

@@ -29,6 +29,9 @@
   <a href="https://opensource.org/licenses/Apache-2.0" title="License: Apache-2.0">
     <img src="https://img.shields.io/badge/License-Apache%202.0-blue.svg">
   </a>
+  <a href="https://www.tickgit.com/browse?repo=github.com/woodpecker-ci/woodpecker" title="TODOs">
+    <img src="https://badgen.net/https/api.tickgit.com/badgen/github.com/woodpecker-ci/woodpecker">
+  </a>
 </p>
 <br/>