WIP: Add "Add Effect" button to Clip Tab

Status Job ID Name Coverage
  Build
failed #358707
build

00:17:07

 
Name Stage Failure
failed
build Build

Passed: 222
Failed: 1
---------
Total: 223
Uploading artifacts...
/builds/yatinmaan/pitivi/xunit.xml: found 1 matching files
Uploading artifacts to coordinator... ok
id=358707 responseStatus=201 Created token=hLkWu7ky
ERROR: Job failed: exit code 1