chore(readme): add installation section

README.md

@@ -19,3 +19,31 @@ For more details, please see --help
 - [x] `vrc-get repo remove <name or url>`
 - [x] `vrc-get repo cleanup`
 - [x] `vrc-get repo packages <NAME|url>`
+
+# Installation
+
+## Using `cargo`
+
+If you have [`cargo`][cargo], installing using cargo is the easiest way to install vrc-get.
+
+```bash
+cargo install --locked --git https://github.com/anatawa12/vrc-get.git --tag <version>
+```
+
+## Prebuilt binaries
+
+There's prebuilt binaries on the [release] page.
+
+Download executable file for your platform and place to everywhere you want.
+There's no additional requirements for thise binaries. All binaries are compiled statically as possible.
+
+For linux, it's a actually static linked executable.
+
+For windows, only `bcrypt.dll`, `ntdll.dll`, `kernel32.dll`, `advapi32.dll`, `ws2_32.dll`, `secur32.dll`, 
+and `crypt32.dll`, which is builtin dlls, are dynamically linked.
+
+For macOS, only `Security.framework`, `CoreFoundation.framework`, `libiconv.2.dylibs`, and `libSystem.B.dylibs`, 
+which are macOS-builtin dylibs, are dynamically linked.
+
+[cargo]: https://github.com/rust-lang/cargo/
+[release]: https://github.com/anatawa12/vrc-get/releases/latest