Implement typed text_transform support with enum-backed combinations

spec/text_transform_spec.cr

@@ -0,0 +1,33 @@
+require "./spec_helper"
+
+module CSS::TextTransformSpec
+  class Style < CSS::Stylesheet
+    rule h1 do
+      text_transform :none
+      text_transform :math_auto
+      text_transform :uppercase
+      text_transform :full_width
+      text_transform :full_size_kana
+      text_transform :lowercase, :full_width
+      text_transform :capitalize, :full_width, :full_size_kana
+    end
+  end
+
+  describe "Style.to_s" do
+    it "renders keyword and combination values" do
+      expected = <<-CSS
+      h1 {
+        text-transform: none;
+        text-transform: math-auto;
+        text-transform: uppercase;
+        text-transform: full-width;
+        text-transform: full-size-kana;
+        text-transform: lowercase full-width;
+        text-transform: capitalize full-width full-size-kana;
+      }
+      CSS
+
+      Style.to_s.should eq(expected)
+    end
+  end
+end

src/css/enums/text_transform.cr

@@ -0,0 +1,7 @@
+css_enum TextTransform do
+  Capitalize
+  Uppercase
+  Lowercase
+  FullWidth
+  FullSizeKana
+end

src/css/enums/text_transform_math_auto.cr

@@ -0,0 +1,3 @@
+css_enum TextTransformMathAuto do
+  MathAuto
+end

src/stylesheet.cr

@@ -1372,7 +1372,9 @@ module CSS
     prop2 text_overflow, CSS::Enums::TextOverflow | String, CSS::Enums::TextOverflow | String
     prop text_rendering, String
     prop text_shadow, String
-    prop text_transform, String
+    prop text_transform, CSS::Enums::None | CSS::Enums::TextTransform | CSS::Enums::TextTransformMathAuto
+    prop2 text_transform, CSS::Enums::TextTransform, CSS::Enums::TextTransform
+    prop3 text_transform, CSS::Enums::TextTransform, CSS::Enums::TextTransform, CSS::Enums::TextTransform
     prop text_underline_offset, String
     prop text_underline_position, String
     prop text_wrap, String