Add search functionality for the asset portal

[JCash]

trafficstars

[FlexYourBrain]

Add search functionality for the asset portal

Describe: Currently users can navigate the asset portal with the use of filters which can help narrow down their search for things they may be looking for. As the asset portal grows these filters may become less useful and users looking for specific things will need to sift through lists of items trying to find what they are looking for. Adding search functionality should make it easier for users to navigate to things they are looking for and scale with the growth of the asset portal submissions.

[britzl]

Added: https://github.com/defold/defold.github.io/commit/f1b2543278b5706c9369dfb71fd8dae8eb8620a8