Add term-rustdoc (#38)

The app is still under development, but the UI is mostly based on
ratatui's Buffer and Block widget.

Specifically I use ratatui to write a built-in generic scrollable area
widget, markdown rendering widget ( [idea
sharing](joshka/tui-markdown#2) ) and treeview
widget.

Ratatui's documentation on the website is really user-friendly and
awesome! I learned to write a TUI from scratch through it. Thank you for
your work.

README.md

@@ -55,6 +55,7 @@ Aside from those listed here, many other apps and libraries can be easily be fou
 - [tui-tree-widget](https://crates.io/crates/tui-tree-widget) - Tree widget for ratatui.
 - [tui-widget-list](https://crates.io/crates/tui-widget-list) - A versatile list implementation for ratatui.
 - [edtui](https://github.com/preiter93/edtui) - A TUI based vim-inspired editor widget for ratatui.
+- [term-rustdoc](https://github.com/zjp-CN/term-rustdoc) - A TUI for Rust docs that aims to improve the UX on tree view and generic code.
 
 ### 🔧 Utilities