golangci-lint configuration file

golangci-lint can run all the currently enabled linters, and as far as I
can tell, does it in under 5 seconds as opposed to over 180 seconds
(compare `time make cilint` and `time make lint`).

Some of the linters that are listed in the "enabled" section but
commented out looked like a good idea to me, and fairly low hanging
fruit to fix, but they are not passing at the moment.

All the linters covered in the current Makefile are run.

TODO:
- replace lint target in Makefile with golangci-lint
- remove .github/workflow/errcheck.yml

app/focus_tracker.go

@@ -200,7 +200,7 @@ func (tracker *FocusTracker) focusables() []wtf.Wtfable {
 	}
 
 	// Sort for deterministic ordering
-	sort.SliceStable(focusable[:], func(i, j int) bool {
+	sort.SliceStable(focusable, func(i, j int) bool {
 		iTop := focusable[i].CommonSettings().Top
 		jTop := focusable[j].CommonSettings().Top
 

app/wtf_app.go

@@ -109,6 +109,7 @@ func (wtfApp *WtfApp) keyboardIntercept(event *tcell.EventKey) *tcell.EventKey {
 		switch string(event.Rune()) {
 		case "/":
 			return nil
+		default:
 		}
 	}