Build PDF using TinyTex

[core-man]

@seisman is working on a GitHub Actions workflow in #264. In that PR, we use TinyTex to build the PDF, but 构建文档 still recommends TexLive. We should recommend TinyTex.

[seisman]

No, we use TinyTeX only because it's smaller and faster for CI purpose.

For most users, they should use TeXLive unless they're LaTeX gurus.