Improve and update documentation: `faq.md`

--

[✔] TOC.md
[✔] crossdomain.md
[ ] css.md
[ ] extend.md
[✔] faq.md
[ ] html.md
[ ] js.md
[ ] misc.md
[ ] usage.md
Improve and update documentation: `css.md`

--

[✔] TOC.md
[✔] crossdomain.md
[✔] css.md
[ ] extend.md
[✔] faq.md
[ ] html.md
[ ] js.md
[ ] misc.md
[ ] usage.md