Added a search field in package-selector.js

[DavidSingh3]

A faster way to filter the plugins or themes list on the "settings > SatisPress" page.

When searching on this page using the browser's search function, plugin and theme names will be found multiple times on the page. This is a bit cumbersome when you have a long list of plugins.

This PR adds a search field in the "manage packages" sidebar, in order to efficiently filter the list of plugins and themes.

The new search field:

• is case-insensitive
• can search through package slug, name, and author name
• supports multiple search terms (divided by a space in the search field)

[DavidSingh3]

an unused "element.Component" import was also removed.

[bradyvercher]

@DavidSingh3 This is pretty cool. Thanks for submitting the PR!