rustup-{set,self,completions,doc,override,component}: add page (#10729)

* rustup set: add page

* rustup self: add page

* rustup completions: add page

* rustup doc: add page

* rustup override: add page

* rustup component: add page

---------

Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>

pages/common/rustup-doc.md

@@ -0,0 +1,25 @@
+# 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`