Bump html-proofer from 3.18.0 to 3.18.2

Bumps html-proofer from 3.18.0 to 3.18.2.

Commits

• 480c471 💎 bump to 3.18.2
• 4ec5831 Merge pull request #612 from gjtorikian/yet-another-broken-hash
• 8f8f0a4 All rubbish
• a555714 Expand the concept of internal
• 92e9d8c Rework this concat a bit
• 59d2344 Don't work like that
• 4eaa9b2 Hash lookup correction
• 893a7cf Demonstrate link problem
• 797970d 💎 bump to 3.18.1
• 626e539 Merge pull request #610 from gjtorikian/external-inner-hash
• Additional commits viewable in compare view