Fix Sidebar scrolling with Admin content

[WiXSL]

Fixes #4684

Before:

After:

[fzaninotto]

this completely breaks the layout on iE11 (which is otherwise pretty well supported)

[adfaris]

Suggested change

	position: 'sticky',
	position: 'fixed',

please take a look at this doc for explanation. https://caniuse.com/#feat=css-fixed

[WiXSL]

I looked at your PR. and try to add

position: 'fixed'

but it breaks the layout.

Also breaks the layout:
position: 'fixed',
top: '4em',
zIndex: 100,

[WiXSL]

It works in the demo because you have a surrounding div, but not when changing the same in the Sidebar's Drawer component

[WiXSL]

Any other suggestions?

[WiXSL]

For anyone interested, I've moved to a different solution in user land:
A Datagrid with scrollable content indirectly solving the movement of the menus.

import * as React from "react";
import { makeStyles } from "@material-ui/core/styles";
import TableContainer from "@material-ui/core/TableContainer";
import { Datagrid } from "react-admin";

const useStyles = makeStyles(
    theme => ({
        container: {
            maxHeight: "70vh"
        }
    })
);

export const ScrollDatagrid = props => {
    const classes = useStyles(props);

    return (
        <TableContainer className={classes.container}>
            <Datagrid
                stickyHeader /* <= Incompatible with IE 11 */
                {...props}
            />
        </TableContainer>
    );
};

[fzaninotto]

I've begun to implement this another way in #6534, so I'll close this PR, which has gone stale.