Fix Plugin Search Filter on Direct Navigation & URL Decoding

[Syncxv]

This PR fixes an issue where navigating directly to a filtered plugin URL (eg. /plugins#query) would fail to apply the filter and instead show the default list of plugins.

It also fixes an issue where URL encoded characters (like spaces becoming %20) were not being decoded when populating the search input from the URL hash.

Steps to Reproduce Filter Bug

1. Go to the plugins page.
2. Search for a term.
3. Reload the page (or open the URL in a new tab).
4. The page loads showing the first alphabetical plugins instead of the search results.

Steps to Reproduce Encoding Bug

1. Search for a term with spaces (e.g. allows you to).
2. Reload the page.
3. The search input would contain allows%20you%20to instead of allows you to