License headers in files generated by `mdbook init --theme`

[mgeisler]

Question

Hello, I have a small question about the use of the files generated by mdbook init --theme. Today, I get

theme
├── book.js
├── css
│   ├── chrome.css
│   ├── general.css
│   ├── print.css
│   └── variables.css
├── favicon.png
├── favicon.svg
├── fonts
│   ├── fonts.css
│   ├── OPEN-SANS-LICENSE.txt
│   ├── open-sans-v17-all-charsets-300italic.woff2
│   ├── open-sans-v17-all-charsets-300.woff2
│   ├── open-sans-v17-all-charsets-600italic.woff2
│   ├── open-sans-v17-all-charsets-600.woff2
│   ├── open-sans-v17-all-charsets-700italic.woff2
│   ├── open-sans-v17-all-charsets-700.woff2
│   ├── open-sans-v17-all-charsets-800italic.woff2
│   ├── open-sans-v17-all-charsets-800.woff2
│   ├── open-sans-v17-all-charsets-italic.woff2
│   ├── open-sans-v17-all-charsets-regular.woff2
│   ├── SOURCE-CODE-PRO-LICENSE.txt
│   └── source-code-pro-v11-all-charsets-500.woff2
├── highlight.css
├── highlight.js
└── index.hbs

The .css, .js, and .hbs files lack copyright headers and I would like to ensure that we're doing the right thing when distributing and modified these files for Comprehensive Rust.

Should I create a PR to add a header? If so, which license do they use?

Version

mdbook v0.4.34