feat: support color dots for 4 character hex.

- Support color dot for 4-letter hex (`#fffa` which is equal to `#ffffffaa`).
- Unit test added.

modules/markup/markdown/color_util.go

@@ -6,7 +6,7 @@ package markdown
 import "regexp"
 
 var (
-	hexRGB = regexp.MustCompile(`^#([0-9a-f]{3}|[0-9a-f]{6}|[0-9a-f]{8})$`)
+	hexRGB = regexp.MustCompile(`^#([0-9a-f]{3,4}|[0-9a-f]{6}|[0-9a-f]{8})$`)
 	hsl    = regexp.MustCompile(`^hsl\([ ]*([012]?[0-9]{1,2}|3[0-5][0-9]|360),[ ]*([0-9]{0,2}|100)\%,[ ]*([0-9]{0,2}|100)\%\)$`)
 	hsla   = regexp.MustCompile(`^hsla\(([ ]*[012]?[0-9]{1,2}|3[0-5][0-9]|360),[ ]*([0-9]{0,2}|100)\%,[ ]*([0-9]{0,2}|100)\%,[ ]*(1|1\.0|0|(0\.[0-9]+))\)$`)
 	rgb    = regexp.MustCompile(`^rgb\(([ ]*((([0-9]{1,2}|100)\%)|(([01]?[0-9]{1,2})|(2[0-4][0-9])|(25[0-5]))),){2}([ ]*((([0-9]{1,2}|100)\%)|(([01]?[0-9]{1,2})|(2[0-4][0-9])|(25[0-5]))))\)$`)

modules/markup/markdown/color_util_test.go

@@ -17,6 +17,7 @@ func TestMatchColor(t *testing.T) {
 		{"#ddeeffa0", true},
 		{"#ddeefe", true},
 		{"#abcdef", true},
+		{"#fffa", true},
 		{"#abcdeg", false},
 		{"#abcdefg0", false},
 		{"black", false},