Introduce kittest for automated UI testing and git-lfs for UI snapshot handling

.gitattributes

@@ -2,3 +2,6 @@
 *.zip -text diff
 Cargo.lock linguist-generated=false
 pixi.lock linguist-generated=true
+
+# git-lfs stuff
+**/snapshots/**/*.png filter=lfs diff=lfs merge=lfs -text

.gitignore

@@ -58,6 +58,8 @@ wheels
 
 # Screenshot comparison build
 /compare_screenshot
+**/tests/snapshots/**/*.diff.png
+**/tests/snapshots/**/*.new.png
 
 *.rrd
 

BUILD.md

@@ -31,6 +31,21 @@ If you are using an Apple-silicon Mac (M1, M2), make sure `rustc -vV` outputs `h
 rustup set default-host aarch64-apple-darwin && rustup install 1.80.0
 ```
 
+## Git-lfs
+
+We use [git-lfs](https://git-lfs.com/) to store big files in the repository, such as UI test snapshots.
+We aim to keep this project buildable without the need of git-lfs (for example, icons and similar assets are checked in to the repo as regular files).
+However, git-lfs is generally required for a proper development environment, e.g. to run tests.
+
+### Setting up git-lfs
+
+The TL;DR is to install git-lfs via your favorite package manager (`apt`, Homebrew, MacPorts, etc.) and run `git lfs install`.
+See the many resources available online more details.
+
+You can ensure that everything is correctly installed by running `git lfs ls-files` from the repository root.
+It should list some test snapshot files.
+
+
 ## Validating your environment
 You can validate your environment is set up correctly by running:
 ```sh