Add icons for new file types.

[AdaRoseCannon]

Perpetual issue for requesting support of an icon or adding support.

Tag this issue in PRs. Add icons todo/done to this comment below

• [x] css
• [x] html
• [x] markdown
• [x] images
• [x] .pdf
• [x] directories
• [x] .html files
• [x] .js files
• [x] package.json
• [ ] .c files
• [ ] .h files
• [ ] .o files
• [ ] .json files
• [ ] ruby files