Add FavoriteFill icon

[naomigrace]

Requesting to add a fill version of the Favorite icon, similar to how Flag has a FlagFill version

[ShimiSun]

For now, here is an example how could that be achieved indirectly to a filled icon https://codesandbox.io/s/o7wjvrj3wy

[naomigrace]

For anyone who comes across this and wants to fill other icons like the Filter icon, you have to look inside the svg to see what selector to use (polygon for the Filter icon).

import styled, { css } from "styled-components";
import { Filter, Favorite } from "grommet-icons";

const filledIcon = css`
  path[fill="none"] {
    fill: rgb(229 36 59) !important;
  }
  polygon[fill="none"] {
    fill: rgb(229 36 59) !important;
  }
`;

export const FavoriteFilled = styled(Favorite)`
  ${(props) => (props.filled ? filledIcon : "")}
`;

export const FilterFilled = styled(Filter)`
  ${(props) => (props.filled ? filledIcon : "")}
`;

[taysea]

Related to #274