Leaderboard Initial Implementation & Several Minor Changes

[Cena-Studio]

Overview

This PR mainly implements the default leaderboard. It also made some adjustments to previous styles

Major Changes

Front End

• app/views/report/index.html.erb is changed.
• app/assets/stylesheets/leaderboard.css and app/javascript/report/index.js are added to provide logics/styles for the leaderboard page.
• Default modules turbo-rails and controllers have been disabled since they caused some unknown bugs.

Back End

• raw_data is roughly implemented to respond with the minimum required JSON data for the default leaderboard.

Minor Changes

• Since the text color #586674 for the navibar looks better than #404040 in most cases, it is now defined as the default font color.
• The background style of the navibar has been changed based on personal preferences. Whether it is better than the previous implementation needs to be evaluated by the reviewer.

Testing

1. Pull this branch and start the server with the command rails s.
2. This PR is shipped with a feasible approach to populate instance reports:
   • Uncomment line 2 to line 20 in app/javascript/report/index.js.
   • Refresh the webpage localhost:3000/leaderboards. A new record should be added to the leaderboard each time the webpage is refreshed until the uncommented lines are disabled again.
3. Once there are enough records. Visit localhost:3000/leaderboards to see the result.

[Cena-Studio]

Fixed the issue that the ranking bar is not rendered with correct length.

[Womblue]

I've just made a commit with some backend changes. They're quite minor, but I'll summarise them here and you can check the commit for the exact lines changed.

• The /leaderboard/:sort_column route has been removed, since it only existed for the purpose of the old sorting method which is deprecated alongside this PR.
• I've included a new method for Report from the branch I'm working on because I think it's useful here. Report#pretty_owner will return a string representing the username of the user who owns that report. The difference between this and simple retrieving username is that pretty_owner will return "Anonymous" if the report was sent without a user. The current leaderboard was showing null in these cases which we should avoid showing to users.
• I've changed the notation used to access the fields of the report table. While it's possible to use (e.g.) report[:ram_units] or report.ram_units to access the same field, the latter is more conventional in Rails. Functionally there is a difference too - if you made a typo and tried to call report[:rm_uits] then you'll get nil as a response, whereas report.rm_uits will raise an error stating that the field doesn't exist.