add docs for addClause() and addBaseClause()

[tabacitu]

I didn't find any place where we had this documented, so here goes:

[pxpm]

Hey @tabacitu thanks for your contribution.
I 100% LOVE this docs and examples you gave. ❤️

We have a little "explanation" about addBaseClause here:

docs/7.x-dev/crud-operation-list-entries.md

Line 247 in c0f76ca

CRUD::addBaseClause('where', 'name', '=', 'car');

I think this would be worth to add in both places (here, in filters) and in the list entries docs. Should I copy this over there too ?

Cheers

[tabacitu]

Ah ok, that's great. That's why it didn't show up in search, because it's in a code block. I think it's fine as it is - people can see it in the ListOperation docs, then they'll search for it if they want more info.

We could have provided a link, though 👀