Add build manifest for Arch & put build status badge in README.md

.builds/arch.yml

@@ -0,0 +1,10 @@
+image: archlinux
+packages:
+  - rust
+sources:
+  - https://git.sr.ht/~tsdh/swayr
+tasks:
+  - build: |
+      cd swayr
+      cargo build
+      cargo clippy

README.md

@@ -55,6 +55,10 @@ and logging are optional.
 
 Bugs and requests can be reported [here](https://todo.sr.ht/~tsdh/swayr).
 
+## Build status
+
+[![builds.sr.ht status](https://builds.sr.ht/~tsdh/swayr.svg)](https://builds.sr.ht/~tsdh/swayr?)
+
 ## License
 
 Swayr is licensed under the