Update CSS at-rule hints (#14013)

* Update CSS at-rules

Add @counter-style and @font-feature-values.
(Align colons.)

* Revert colon aligment

* Make CSS at-rule descriptions bit more consistent

* Fix the unit test for CSS At-Rule Hints

Author: valtlai

src/extensions/default/CSSAtRuleCodeHints/AtRulesDef.json

@@ -1,10 +1,12 @@
 {
-    "@charset":   "Defines the character set used by the style sheet.",
-    "@import":    "Tells the CSS engine to include an external style sheet.",
-    "@namespace": "Tells the CSS engine that all its content must be considered prefixed with an XML namespace.",
-    "@media":     "A conditional group rule which will apply its content if the device meets the criteria of the condition defined using a media query.",
-    "@supports":  "A conditional group rule which will apply its content if the browser meets the criteria of the given condition.",
-    "@page":      "Describes the aspect of layout changes which will be applied when printing the document.",
-    "@font-face": "Describes the aspect of an external font to be downloaded.",
-    "@keyframes": "Describes the aspect of intermediate steps in a CSS animation sequence."
+    "@charset":             "Defines the character set used by the style sheet.",
+    "@counter-style":       "Defines specific counter styles that are not part of the predefined set of styles.",
+    "@font-face":           "Describes the aspect of an external font to be downloaded.",
+    "@font-feature-values": "Defines common names in font-variant-alternates for feature activated differently in OpenType.",
+    "@import":              "Tells the CSS engine to include an external style sheet.",
+    "@keyframes":           "Describes the aspect of intermediate steps in a CSS animation sequence.",
+    "@media":               "A conditional group rule which will apply its content if the device meets the criteria of the condition defined using a media query.",
+    "@namespace":           "Tells the CSS engine that all its content must be considered prefixed with an XML namespace.",
+    "@page":                "Describes the aspect of layout changes which will be applied when printing the document.",
+    "@supports":            "A conditional group rule which will apply its content if the browser meets the criteria of the given condition."
 }

src/extensions/default/CSSAtRuleCodeHints/unittests.js

@@ -141,7 +141,9 @@ define(function (require, exports, module) {
                     var hintList = expectHints(CSSAtRuleCodeHints.restrictedBlockHints);
                     verifyFirstEntry(hintList, "@charset");  // filtered on "empty string"
                     verifyListsAreIdentical(hintList, ["@charset",
+                                                       "@counter-style",
                                                        "@font-face",
+                                                       "@font-feature-values",
                                                        "@import",
                                                        "@keyframes",
                                                        "@media",