update installation and updating docs

Author: ellie

Diff for: src/content/docs/guide/installation.mdx

@@ -211,8 +211,9 @@ After installing, remember to restart your shell.
 
 ## Upgrade
 
-In order to upgrade Atuin, just run the installation script again! It won't add to
-your shell config more than once, so is safe to re-run.
+Run `atuin-update`, and if that command is not available, run the install script again.
+
+If you used a package manager to install Atuin, then you should also use your package manager to update Atuin.
 
 ## Uninstall
 

Diff for: src/content/docs/uninstall.md

@@ -4,12 +4,18 @@ title: Uninstalling Atuin
 
 Sorry to see you go!
 
-Uninstalling Atuin depends on your system, and how you installed it. Wherever possible, our install script will use your system package manager.
+If you used the Atuin installer, you can totally delete it by removing the following
+
+1. Delete the ~/.atuin directory
+2. Delete the ~/.local/share/atuin directory
+3. Remove the line referencing "atuin init" from your shell config
+
+Otherwise, uninstalling Atuin depends on your system, and how you installed it. 
 
 EG, on macOS, you'd want to run
 
 ```
 brew uninstall atuin
 ```
 
-There is also a shell integration that you will need to remove from your shell config file. Find the line referencing `atuin init` , and remove it.
+and then remove the shell integration.