Monitor shared repos (#5375)

* [shared with me] added 'watch/unwatch file changes' for libraries

* [groups, group] added 'watch/unwatch file changes' for libraries

* [shared with me] only libraries shared with 'r', 'rw' permissions can be monitored

* [groups, group] only libraries shared with 'r', 'rw' permissions can be monitored

* [shared with me] improved the interaction for library items

* [groups, group] cleaned up the code

frontend/src/components/repo-monitored-icon.js

@@ -0,0 +1,33 @@
+import React, { Fragment } from 'react';
+import PropTypes from 'prop-types';
+import { UncontrolledTooltip } from 'reactstrap';
+import Icon from '../components/icon';
+import { gettext } from '../utils/constants';
+
+const propTypes = {
+  repoID: PropTypes.string.isRequired
+};
+
+class RepoMonitoredIcon extends React.Component {
+
+  render() {
+    const { repoID } = this.props;
+    return (
+      <Fragment>
+        <span id={`watching-${repoID}`} className="ml-1">
+          <Icon symbol='monitor' />
+        </span>
+        <UncontrolledTooltip
+          placement="bottom"
+          target={`#watching-${repoID}`}
+        >
+          {gettext('You are watching file changes of this library.')}
+        </UncontrolledTooltip>
+      </Fragment>
+    );
+  }
+}
+
+RepoMonitoredIcon.propTypes = propTypes;
+
+export default RepoMonitoredIcon;