[Docs] Add documentation for the AgGrid

[maxschulz-COL]

Description

This PR contains the documentation for the AG Grid feature - it replaces https://github.com/mckinsey/vizro/pull/269.

This PR contains the code changes from https://github.com/mckinsey/vizro/pull/289 - so any changes inside src/vizro can be ignore as that PR will be reviewed separately and merge before this one

Open ToDos

• [x] Exchange Screenshots
• [x] Update feature dashboard and yaml

@AnnMarieW I took your stylings on the CSS PR as an example on how to style and individual AG Grid - the "advanced" docs examples. Thanks!

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[maxschulz-COL]

• Do a find of "table" in the docs on AG Grid to make sure there's no left over copy and paste errors

I could not really find any, were there any specific ones you had in mind?

• Make sure we are consistent with "AG Grid" over "AGGrid" etc.

I decided now for AG Grid instead of AGGrid as it seems the more popular choice

• Make sure the docs are up to date with whatever names we ultimately use in the code

Yes, I anticipated AGGrid when writing, but we have changed to AgGrid so changed it just now