[docs] Start documentation for the data grid filter features

[dtassone]

Related to #201

WIP structure:

# Data Grid - Filtering

## Column filters

By default, when filtering is enabled.

### Basic filter

Per-column with 3 types: string, number, date/time.

<DataGrid /> open by default for the demo, enabled by default.

### Disable filter

- globally

<DataGrid />

- per column filterable: boolean

<DataGrid />

Benchmark
https://master--material-ui-x.netlify.app/components/data-grid/rows/#disable-sorting
https://ag-grid.com/javascript-grid-filtering/#configuring-filters-on-columns

### Custom filter operator

Demo ideas with Airtable rating ⭐️⭐️⭐️⭐️ or slider progress/quantity.

<DataGrid />

Benchmark
https://www.telerik.com/kendo-react-ui/components/grid/filtering/#toc-custom-filter-operators
https://devexpress.github.io/devextreme-reactive/react/grid/docs/guides/filtering/#custom-filter-operations

### Toolbar

How to enable and use the toolbar

### Server-side filter

<DataGrid />

Benchmark
https://master--material-ui-x.netlify.app/components/data-grid/rows/#server-side-sorting
https://devexpress.github.io/devextreme-reactive/react/grid/docs/guides/filtering/#remote-filtering

### Controlled filtering

<DataGrid />

https://master--material-ui-x.netlify.app/components/data-grid/pagination/#controlled-pagination

### Multi-filtering ⚡️

<XGrid />

### apiRef ⚡️

https://master--material-ui-x.netlify.app/components/data-grid/rows/#apiref

## Quick filter

[oliviertassinari]

Great start, I really appreciate that have you split the work into multiple chunks! It seems that you have focused here on doing half of the structure drawn in #644 :)

• We can remove the 🚧 icon liked to the filtering feature: in the side nav and in the feature comparison

• One of the new demo turns my CPU into a 🍳 maker

[oliviertassinari]

Why remove this section? Don't we still want to implement quick filtering?

[dtassone]

Yes but we can add it later...

Just wanted to cleanup the page, but I can put it back, not an issue :)

[oliviertassinari]

From my perspective, it depends on the following: do we want to implement this feature no matter what, and do we think it's important?

If the answer is yes to these two conditions, then I think we should keep linking the issue so we can use it to prioritize the roadmap. If the answer is no, then we probably want to remove the link, to no skewed the 👍 on the linked issue more.

[dtassone]

We could also add a new page with all the issues in progress so ppl can upvote issues from a central location

[oliviertassinari]

a new page with all the issues in progress

I think it's the option 2 mentioned before. We have this page, it's GitHub's issues, that we could maybe link a bit better, by mentioning it in the roadmap page: https://material-ui.com/discover-more/roadmap/.

[dtassone]

Great start, I really appreciate that have you split the work into multiple chunks! It seems that you have focused here on doing half of the structure drawn in #644 :)

• We can remove the 🚧 icon liked to the filtering feature: in the side nav and in the feature comparison

• One of the new demo turns my CPU into a 🍳 maker

Yes I noticed some issues as well but it does not seem to occur all the time, I'm investigating