Fixed more input accessibility issues, also

- Added searchParams based router for easier testing
 - Added more stories to the storybook

src/components/_FieldSource.jsx

@@ -0,0 +1,37 @@
+import React from 'react'
+import PropTypes from 'prop-types'
+
+import {latest} from '@mapbox/mapbox-gl-style-spec'
+import Block from './Block'
+import FieldAutocomplete from './FieldAutocomplete'
+
+export default class BlockSource extends React.Component {
+  static propTypes = {
+    value: PropTypes.string,
+    wdKey: PropTypes.string,
+    onChange: PropTypes.func,
+    sourceIds: PropTypes.array,
+    error: PropTypes.object,
+  }
+
+  static defaultProps = {
+    onChange: () => {},
+    sourceIds: [],
+  }
+
+  render() {
+    return <Block
+      label={"Source"}
+      fieldSpec={latest.layer.source}
+      error={this.props.error}
+      data-wd-key={this.props.wdKey}
+    >
+      <FieldAutocomplete
+        value={this.props.value}
+        onChange={this.props.onChange}
+        options={this.props.sourceIds.map(src => [src, src])}
+      />
+    </Block>
+  }
+}
+