refactor: focus around Render/Compact/Pretty/NewWith functions

This is yet another drastic refactor of public API and concepts.
Hopefully the last one, as I'm now fairly happy with things.

yaml_test.go

@@ -24,7 +24,7 @@ func TestYAML_Render(t *testing.T) {
 	tests := []struct {
 		name      string
 		indent    int
-		value     interface{}
+		value     any
 		want      string
 		wantErr   string
 		wantErrIs []error
@@ -113,3 +113,9 @@ func TestYAML_Render(t *testing.T) {
 		})
 	}
 }
+
+func TestYAML_Formats(t *testing.T) {
+	h := &YAML{}
+
+	assert.Equal(t, []string{"yaml", "yml"}, h.Formats())
+}