Add error handling to benchmark branch.

[cesutherland]

Add error handling to hopefully save someone a couple minutes.

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I ran the benchmark against v2.0.0-next.7 and the suite failed successfully. Adding error handling revealed an error on html comments <!-- … from remark-mdx. (Removing the comment, the benchmark on v2 clocks in exactly where 1.6 did!)

$ yarn start
yarn run v1.22.4
$ node .
[122:2: Unexpected character `!` (U+0021) before name, expected a character that can start a name, such as a letter, `$`, or `_`] {
  message: 'Unexpected character `!` (U+0021) before name, expected a character that can start a name, such as a letter, `$`, or `_`',
  name: '122:2',
  reason: 'Unexpected character `!` (U+0021) before name, expected a character that can start a name, such as a letter, `$`, or `_`',
  line: 122,
  column: 2,
  location: {
    start: { line: 122, column: 2, offset: 2598, index: 1 },
    end: { line: null, column: null }
  },
  source: 'remark-mdx',
  ruleId: 'unexpected-character',
  fatal: true
}
error Command failed with exit code 1.

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[johno]

Thanks!