Add add-ons and contributing sections

README.md

@@ -131,3 +131,47 @@ screens.
 Arrange screens vertically to prevent windows from bleeding into other screens.
 
 <img width="780" alt="Screen Shot 2022-01-07 at 14 18 27" src="https://user-images.githubusercontent.com/900731/148595785-546f9086-9add-4731-8477-233b202378f4.png">
+
+## Add-ons
+
+The following Spoons compliment PaperWM.spoon nicely.
+
+- [ActiveSpace.spoon](https://github.com/mogenson/ActiveSpace.Spoon) Show active and layout of Mission Control spaces in the menu bar.
+- [Swipe.spoon](https://github.com/mogenson/Swipe.spoon) Perform actions when trackpad swipe gestures are recognized. Here's an example config to change PaperWM.spoon focused window:
+```lua
+-- focus adjacent window with 3 finger swipe
+local current_id, threshold
+Swipe = hs.loadSpoon("Swipe")
+Swipe:start(3, function(direction, distance, id)
+    if id == current_id then
+        if distance > threshold then
+            threshold = math.huge -- trigger once per swipe
+
+            -- use "natural" scrolling
+            if direction == "left" then
+                PaperWM.actions.focus_right()
+            elseif direction == "right" then
+                PaperWM.actions.focus_left()
+            elseif direction == "up" then
+                PaperWM.actions.focus_down()
+            elseif direction == "down" then
+                PaperWM.actions.focus_up()
+            end
+        end
+    else
+        current_id = id
+        threshold = 0.2 -- swipe distance > 20% of trackpad size
+    end
+end)
+```
+
+## Contributing
+
+Contributions are welcome! Here are a few preferences:
+- Global variables are `CamelCase` (eg. `PaperWM`)
+- Local variables are `snake_case` (eg. `local focused_window`)
+- Function names are `lowerCamelCase` (eg. `function windowEventHandler()`)
+- Use `<const>` where possible
+- Create a local copy when deeply nested members are used often (eg. `local Watcher <const> = hs.uielement.watcher`)
+
+Code format checking and linting is provided by [lua-language-server](https://github.com/LuaLS/lua-language-server) for commits and pull requests. Run `lua-language-server --check=init.lua` locally before commiting.