Marketplace: Add a Paid/Free filter

[Robertght]

What

I noticed we have Free and Paid/Premium plugins, therefore it would be a really nice addition to be able to filter the plugins based on the Free/Paid(Premium) state.

Why

This could help users find the needed functionality and quickly gain access to Premium plugins features.

How

Rought example:

[allilevine]

This seems like it would be low impact after https://github.com/Automattic/wp-calypso/pull/61102 and https://github.com/Automattic/wp-calypso/pull/61098 make it easier to access the free plugin list.

[gcsecsey]

@SaxonF do you think we should still pursue this? If so, could you help with the filter desings?

[SaxonF]

We've been looking at filtering patterns as part of the theme showcase work which would also be appropriate here pdh6GB-Jz-p2. Work on plugin category filter has already started so when the time is right we can also introduce a price filter if it makes sense.

[cpapazoglou]

@SaxonF can adjust this to the current Plugins page? Will we minimise the categories width so that we can accommodate the filters?

[cpapazoglou]

Or we can add the filter only in search results

[epeicher]

Backlog grooming discussion: We can approach this task filtering in the front end based on the endpoint used. This will also add the UI component. Once we've got free and paid results served from Elasticsearch we can create another task and switch to filter in the backend