Handle JS libraries with webpack

[stopnoanime]

Testing guide:

git fetch https://github.com/stopnoanime/oioioi.git webpack-libs:webpack-libs-test
git switch webpack-libs-test
./easy_toolbox.py down
./easy_toolbox.py build
./easy_toolbox.py up 
# wait for migrations to run
./easy_toolbox.py run

Changes:

• Bump jQuery to 1.12.4
• Update clipboard to latest verison
• Update highlight.js to latest version
• Update marked to latest version
• Update highchart.js to 4.1.10 (lowest version on npm)
• Use js-cookie instead of depreciated jquery-cookie
• Remove unused libs: jquery.storageapi, jquery-ui
• Make ColorWidget use native color input
• Added ESLint config
• Make ./easy_toolbox.py run command run django and webpack concurrently
• Cypress: Fixed bug in cypress github action that causes the workflow to pass if the webserver did not start
• Added webpack and JS related docs

Won't fix for now:

• bootstrap-datetimepicker-oioioi: It is currently only used in DateTimePicker widget and timeline.js. The DateTimePicker widget is broken, unecessary and almost unused (It is used in only one place which can be replaced with the built in django admin datetimepicker or the native browser datetimepicker). Will remove it in separate PR.
• timeline.js: It needs to be slightly modified to remove the dependency on bootstrap-datetimepicker-oioioi. Also there are some other issues with it. Will fix in separate PR.
• ESLint: It found multiple issues in the codebase. Good material for a separate PR.
• Liveranking module: Its dependencies are completely separate, so it can be modernized in a separate PR

Manual testing plan:

• Clipboard.js: Test 'btn-copy' buttons
• Bootstrap tooltips
• Markdown editor, and code block highlighting in generated markdown: Used in portals
• Bootstrap typeahead: Used in login as user form
• Highcharts: Used in contest Statistics
• js-cookie instead of jquery-cookie: Used for example in lagnauge picker
• New color widget
• Portal tree: need to enable portals
• General functionality