Fix build failure on github 2.0

Author: jahn96

.eslintrc.js

@@ -3,7 +3,8 @@ module.exports = {
  'eslint:recommended',
  'plugin:@typescript-eslint/eslint-recommended',
  'plugin:@typescript-eslint/recommended',
- 'plugin:prettier/recommended'
+ 'plugin:prettier/recommended',
+ 'plugin:react/recommended'
  ],
  parser: '@typescript-eslint/parser',
  parserOptions: {

src/CodeSnippetDisplay.tsx

@@ -255,7 +255,7 @@ export class CodeSnippetDisplay extends React.Component<
  <div
  className="triangle"
  title="Bookmark"
- onClick={event => {
+ onClick={(event): void => {
  this.bookmarkSnippetClick(codeSnippet, event);
  }}
  ></div>