Set codecov upload token

Docs seem to indicate this should only be required for private
repos, but we have builds failing claiming this needs to be
specified, so just set it manually.

Author: TheBlueMatt

.github/workflows/build.yml

@@ -71,6 +71,10 @@ jobs:
         if: matrix.coverage
         uses: codecov/codecov-action@v1
         with:
+          # Could you use this to fake the coverage report for your PR? Sure.
+          # Will anyone be impressed by your amazing coverage? No
+          # Maybe if codecov wasn't broken we wouldn't need to do this...
+          token: f421b687-4dc2-4387-ac3d-dc3b2528af57
           fail_ci_if_error: true
 
   fuzz: