Move pages under tldr, lint run.sh, update docs

tldr/rustup-update

@@ -0,0 +1,17 @@
+---
+syntax: markdown
+tags: [tldr, common]
+source: https://github.com/tldr-pages/tldr.git
+---
+# rustup update
+
+> Update Rust toolchains and `rustup` itself (if not installed using a package manager).
+> More information: <https://rust-lang.github.io/rustup>.
+
+- Update all installed toolchains and `rustup`:
+
+`rustup update`
+
+- Install or update a specific toolchain (see `rustup help toolchain` for more information):
+
+`rustup update {{toolchain}}`