Shorten categorical palette URLs

[ShrimpCryptid]

Use Case

Currently, if any color has changed in the categorical palette, the entire palette will be saved to the URL. This is pretty inefficient, considering that users could just be modifying one or two colors out of the 12 colors in a preset palette.

ex: "?palette=000000-000010-000020-000030-000040-000050-000060-000070-000080-000090-0000a0-0000b0"

Saving the closest palette preset AND only the colors that have changed would make this URL shorter and more human-readable. We could insert empty strings for any color that has not changed from the preset.
ex: ?palette-key=adobe&palette=--000020-00030--------
ex: ?palette-key=adobe&palette=--000020-00030 (Truncating extra - separators)

Acceptance Criteria

• Add a utility method to find the closest preset match and return an array of changed colors from it
• Update url_utils to show changes from a palette-key if only some colors have changed.
• Update unit tests.

Details