fix: change getAsset to not return a promise (#3232)

* fix: change getAsset to not return a promise

* fix: update markdown widget per getAsset changes

* test: fix editor component image test

* docs: update getAsset docs

packages/netlify-cms-ui-default/src/Asset.js

@@ -1,50 +0,0 @@
-import React from 'react';
-import PropTypes from 'prop-types';
-
-class Asset extends React.Component {
-  static propTypes = {
-    path: PropTypes.string.isRequired,
-    getAsset: PropTypes.func.isRequired,
-    component: PropTypes.elementType.isRequired,
-    folder: PropTypes.string,
-  };
-
-  subscribed = true;
-
-  state = {
-    value: null,
-  };
-
-  async _fetchAsset() {
-    const { getAsset, path, folder } = this.props;
-    const value = await getAsset(path, folder);
-    if (this.subscribed) {
-      this.setState({ value });
-    }
-  }
-
-  componentDidMount() {
-    this._fetchAsset();
-  }
-
-  componentWillUnmount() {
-    this.subscribed = false;
-  }
-
-  componentDidUpdate(prevProps) {
-    if (
-      prevProps.path !== this.props.path ||
-      prevProps.getAsset !== this.props.getAsset ||
-      prevProps.folder !== this.props.folder
-    ) {
-      this._fetchAsset();
-    }
-  }
-
-  render() {
-    const { component, ...props } = this.props;
-    return React.createElement(component, { ...props, value: this.state.value });
-  }
-}
-
-export default Asset;

packages/netlify-cms-ui-default/src/index.js

@@ -9,7 +9,6 @@ import AuthenticationPage from './AuthenticationPage';
 import WidgetPreviewContainer from './WidgetPreviewContainer';
 import ObjectWidgetTopBar from './ObjectWidgetTopBar';
 import GoBackButton from './GoBackButton';
-import Asset from './Asset';
 import {
   fonts,
   colorsRaw,
@@ -56,7 +55,6 @@ export const NetlifyCmsUiDefault = {
   effects,
   reactSelectStyles,
   GlobalStyles,
-  Asset,
 };
 export {
   Dropdown,
@@ -89,5 +87,4 @@ export {
   reactSelectStyles,
   GlobalStyles,
   GoBackButton,
-  Asset,
 };