docs(installation): add advanced installation (#1643)

Adds an "Advanced Installation" page to the documentation website.

README.md

@@ -139,6 +139,9 @@
 
 ### Getting Started
 
+**Note**: due to the proliferation of different platforms, only a subset of supported platforms are
+shown below. Can't see yours? Have a look at the [extra platform instructions](https://starship.rs/installing/).
+
 1. Install the **starship** binary:
 
    #### Install Latest Version
@@ -149,15 +152,9 @@
    curl -fsSL https://starship.rs/install.sh | bash
    ```
 
-   ##### From source on [crates.io](https://crates.io/):
-
-   ```sh
-   cargo install starship
-   ```
-
    #### Install via Package Manager
 
-   ##### With [Homebrew](https://brew.sh/):
+   ##### Example: [Homebrew](https://brew.sh/):
 
    ```sh
    brew install starship
@@ -169,7 +166,7 @@
    scoop install starship
    ```
 
-1. Add the init script to your shell's config file:
+2. Add the init script to your shell's config file:
 
    #### Bash
 

docs/.vuepress/config.js

@@ -90,6 +90,7 @@ module.exports = {
         sidebar: [
           "/",
           ["/guide/", "Guide"],
+          ["/installing/", "Advanced Installation"],
           ["/config/", "Configuration"],
           ["/advanced-config/", "Advanced Configuration"],
           ["/faq/", "Frequently Asked Questions"],

docs/installing/README.md

@@ -0,0 +1,52 @@
+# 🚀 Advanced Installation
+
+To install starship, you need to do two things:
+
+1. Get the **starship** binary onto your computer
+1. Tell your shell to use the starship binary as its prompt by modifying its init scripts
+
+For most users, the instructions on [the main page](/guide/#🚀-installation) will work great. However,
+for some more specialized platforms, different instructions are needed.
+
+There are so many platforms out there that they didn't fit into the main
+README.md file, so here are some installation instructions for other platforms
+from the community. Is yours not here? Please do add it here if you figure it
+out!
+
+## [Nix](https://nixos.wiki/wiki/Nix)
+
+### Getting the Binary
+
+#### Imperatively
+
+```sh
+nix-env -iA nixos.starship
+```
+
+#### Declarative, single user, via [home-manager](home-manager)
+
+Add `pkgs.starship` to your `home.packages` in your `home.nix` file, then run
+
+```sh
+home-manager switch
+```
+
+#### Declarative, system-wide, with NixOS
+
+Add `pkgs.starship` to `environment.packages` in your `configuration.nix`,
+then run
+
+```sh
+sudo nixos-rebuild switch
+```
+
+### Modifying Init Scripts
+
+#### With Nix and home-manager, using zsh:
+
+Add the following to `programs.zsh.initExtra` in your `home.nix` file, then
+run
+
+```sh
+home-manager switch
+```