move author name colouring code into its own file

pkg/gui/presentation/authors/authors_test.go

@@ -0,0 +1,20 @@
+package authors
+
+import "testing"
+
+func TestGetInitials(t *testing.T) {
+	for input, expectedOutput := range map[string]string{
+		"Jesse Duffield":     "JD",
+		"Jesse Duffield Man": "JD",
+		"JesseDuffield":      "Je",
+		"J":                  "J",
+		"六书六書":               "六",
+		"書":                  "書",
+		"":                   "",
+	} {
+		output := getInitials(input)
+		if output != expectedOutput {
+			t.Errorf("Expected %s to be %s", output, expectedOutput)
+		}
+	}
+}