Update dependency katex to ^0.18.4 - #272

Changed pages include:

• index.html - view
• 404.html - view
• contributing/index.html - view
• examples/css-icons/index.html - view
• examples/custom-fonts/index.html - view
• examples/custom-title-link/index.html - view
• examples/directory-index/index.html - view
• examples/edit-in-editor-button/index.html - view
• examples/git-authors/index.html - view
• examples/git-changelog/index.html - view

There are more changes not included in the list