feat: search by tag, upload page makeover, plus some more

[axiand]

Full list of changes:

• A search box has been added to the right sidebar. For the initial implementation, this simply redirects to the appropriate tag page, replacing spaces with underscores where necessary
• The upload page has been given a large makeover to improve usability
• • Added hints to options to explain how to use them
• • Tags will now be normalized to all-lowercase automatically to maintain consistency
• Improved how tags display to the end user - dashes and underscores are replaced with spaces
• All relevant changes were also translated to Polish ahead of time

[purifetchi]

such a good changeset!!! thank you so much for contributing!!!!!!!!!!!!!