Update cheatsheets

rustup-doc

@@ -0,0 +1,30 @@
+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# rustup doc
+
+> Open the offline Rust documentation for the current toolchain.
+> There are a lot more documentation pages not mentioned here. See `rustup help doc` for more information.
+> More information: <https://rust-lang.github.io/rustup>.
+
+- Open the main page:
+
+`rustup doc`
+
+- Open the documentation for a specific topic (a module in the standard library, a type, a keyword, etc.):
+
+`rustup doc {{std::fs|usize|fn|...}}`
+
+- Open the Rust Programming Language book:
+
+`rustup doc --book`
+
+- Open the Cargo book:
+
+`rustup doc --cargo`
+
+- Open the Rust Reference:
+
+`rustup doc --reference`