Don't trigger CI on Github if only Markdown files changed

I pushed a PR to update the readme and it seems ridiculous to me that the PR has to wait days until the CI can test the entire swift project just for this change.

According to this git - Jenkins: Don't build if only README changed - Stack Overflow it should be possible to exclude files from triggering or requiring a CI build.

Wouldn't that make sense and get rid of lots of completely useless CI builds? That would reduce load on the CI servers.

/cc @tkremenek


We are working on adding a feature to Swift CI pull request testing to avoid building for Markdown files. I don’t have a ETA yet, but I will update this topic soon as we have it.