Improve logging

Everything that gets logged now has a log level associated with it.

The log level can be set with the new `-l` or `--log-level` arguments.

The defaul log level is `debug` for now. There aren't many things that get
logged but if the logs get spammed in the future it can be set down to `info`.

src/invidious/routes/watch.cr

@@ -62,7 +62,7 @@ class Invidious::Routes::Watch < Invidious::Routes::BaseRoute
     rescue ex : VideoRedirect
       return env.redirect env.request.resource.gsub(id, ex.video_id)
     rescue ex
-      logger.puts("#{id} : #{ex.message}")
+      logger.error("get_video: #{id} : #{ex.message}")
       return error_template(500, ex)
     end