Scope and purpose

tablesorter.js used in the thresholds threshold table and useradmin API-token table sorts date columns by their string value and not their numeric time value.

This PR makes it so that date columns are sorted by their numeric time value in these tables.

Urls:
/useradmin/tokens/
/threshold/

This pull request

• Adds a new javascript file that adds a parser (for changing date strings to numeric time value) to the global $.tablesorter object. In contrast to the built-in parsers, this parser looks for a specific node attribute, instead of a node's text value.
• Makes date columns in the thresholds threshold-table and useradmin API-token table use the new parser.
• Disables sorting the last column in the thresholds threshold-table since it is just a column with icons.

Contributor Checklist

• Added a changelog fragment for towncrier
• Added/amended tests for new/changed code
• Added/changed documentation
• Linted/formatted the code with black and ruff, easiest by using pre-commit
• The first line of the commit message continues the sentence "If applied, this commit will ...", starts with a capital letter, does not end with punctuation and is 50 characters or less long. See https://cbea.ms/git-commit/
• This pull request is based on the correct upstream branch: For a patch/bugfix affecting the latest stable version, it should be based on that version's branch (<major>.<minor>.x). For a new feature or other additions, it should be based on master.
• If applicable: Created new issues if this PR does not fix the issue completely/there is further work to be done
• If this results in changes in the UI: Added screenshots of the before and after
• If this adds a new Python source code file: Added the boilerplate header to that file