Added “Unique podcasts” filter for episode search

Sometimes, you want to know what podcasts publish any episodes with certain keywords, but you don’t care what episodes. In this case, you don’t want to see multiple episodes from the same podcast.

Here you go: “unique podcasts” filter! Example:

The “unique podcasts” filter also works in our Datasets product:

https://www.listennotes.com/podcast-datasets/keyword/