Implement user_select

spec/user_select_spec.cr

@@ -0,0 +1,53 @@
+require "./spec_helper"
+
+module CSS::UserSelectSpec
+  class Style < CSS::Stylesheet
+    rule p do
+      user_select :auto
+    end
+
+    rule span do
+      user_select :text
+    end
+
+    rule div do
+      user_select :none
+    end
+
+    rule section do
+      user_select :contain
+    end
+
+    rule article do
+      user_select :all
+    end
+  end
+
+  describe "Style.to_s" do
+    it "renders supported user-select values" do
+      expected = <<-CSS
+      p {
+        user-select: auto;
+      }
+
+      span {
+        user-select: text;
+      }
+
+      div {
+        user-select: none;
+      }
+
+      section {
+        user-select: contain;
+      }
+
+      article {
+        user-select: all;
+      }
+      CSS
+
+      Style.to_s.should eq(expected)
+    end
+  end
+end

src/css/enums/user_select.cr

@@ -0,0 +1,7 @@
+css_enum UserSelect do
+  Auto
+  Text
+  None
+  Contain
+  All
+end

src/stylesheet.cr

@@ -1304,7 +1304,7 @@ module CSS
     prop transition_timing_function, String
     prop translate, String
     prop unicode_bidi, String
-    prop user_select, String
+    prop user_select, CSS::Enums::UserSelect
     prop vector_effect, String
     prop vertical_align, CSS::LengthPercentage | CSS::Enums::VerticalAlign
     prop view_transition_class, String