List Pop!_Shell branches for various Ubuntu versions (#1252)

* shell: List branches for different Ubuntu versions

* shell: Other minor grammar fixes

* shell: Mark code block type

content/pop-shell.md

@@ -23,16 +23,25 @@ sudo apt install git node-typescript make gnome-shell-extension-prefs
 
 **Note:** these instructions assume an Ubuntu-based distro; other distributions (see examples below) will use different package managers, and may have different package names.
 
-Next we'll clone the repository using this command:
+Next, we'll clone the repository and enter the directory using these commands:
 
 ```bash
 git clone https://github.com/pop-os/shell.git
+cd shell
 ```
 
-Now we'll enter the directory for <u>Pop Shell</u> (called "shell") and build the package:
+Then, check out the appropriate branch for your version of Ubuntu. Not all Ubuntu codenames are listed; if your version isn't listed, use the closest version _before_ it in alphabetical order.
+
+```bash
+git checkout master_focal # For Ubuntu 20.04, 20.10, 21.04, and 21.10.
+git checkout master_jammy # For Ubuntu 22.04, 22.10, and 23.04.
+git checkout master_mantic # For Ubuntu 23.10.
+git checkout master_noble # For Ubuntu 24.04, 24.10, and later versions.
+```
+
+Finally, we'll enter the directory for <u>Pop Shell</u> (called "shell") and build the package:
 
 ```bash
-cd shell
 make local-install
 ```
 
@@ -50,13 +59,13 @@ sudo dnf install gnome-shell-extension-pop-shell
 
 <u>Pop Shell</u> is packaged in the AUR, but for the keyboard shortcuts to work, you will need to build it from source like we did above.
 
-In order to build Pop Shell from source we'll first need to install the build dependencies and <u>git</u> to clone the repository:
+In order to build Pop Shell from source, we'll first need to install the build dependencies and <u>git</u> to clone the repository:
 
 ```bash
 sudo pacman -S git typescript make
 ```
 
-Next we'll clone the repository using this command:
+Next, we'll clone the repository using this command:
 
 ```bash
 git clone https://github.com/pop-os/shell.git
@@ -94,4 +103,4 @@ gsettings set org.gnome.mutter overlay-key ''
 sudo pamac install gnome-shell-extension-pop-shell
 ```
 
-To learn about <u>Pop Shell</u>'s keyboard shortcuts you can view this [support article](/articles/pop-keyboard-shortcuts/). You can also view <u>Pop Shell</u>'s source code [here](https://github.com/pop-os/shell).
+To learn about <u>Pop Shell</u>'s keyboard shortcuts, you can view this [support article](/articles/pop-keyboard-shortcuts/). You can also view <u>Pop Shell</u>'s source code [here](https://github.com/pop-os/shell).