Fix tokenizing !important (#1585)

Updates the regex to ensure that when `!important` sits next
to a property with no spaces, it's still tokenized correctly.

components/prism-css.js

@@ -14,7 +14,7 @@ Prism.languages.css = {
 		greedy: true
 	},
 	'property': /[-_a-z\xA0-\uFFFF][-\w\xA0-\uFFFF]*(?=\s*:)/i,
-	'important': /\B!important\b/i,
+	'important': /!important\b/i,
 	'function': /[-a-z0-9]+(?=\()/i,
 	'punctuation': /[(){};:]/
 };
@@ -49,4 +49,4 @@ if (Prism.languages.markup) {
 			alias: 'language-css'
 		}
 	}, Prism.languages.markup.tag);
-}
+}

examples/prism-css.html

@@ -7,7 +7,13 @@ <h2>Simple rule</h2>
 <pre><code>p { color: red; }</code></pre>
 
 <h2>Important rule</h2>
-<pre><code>p { color: red !important; }</code></pre>
+<pre><code>
+p {
+    color: red !important;
+    line-height: normal!important;
+}
+p{position:absolute!important}
+</code></pre>
 
 <h2>@ rule</h2>
 <pre><code>@media screen and (min-width: 100px) {}</code></pre>
@@ -25,4 +31,4 @@ <h2>String</h2>
 <pre><code>content: 'foo';</code></pre>
 
 <h2>URL</h2>
-<pre><code>content: url(foo.png);</code></pre>
+<pre><code>content: url(foo.png);</code></pre>

prism.js

@@ -647,7 +647,7 @@ Prism.languages.css = {
 		greedy: true
 	},
 	'property': /[-_a-z\xA0-\uFFFF][-\w\xA0-\uFFFF]*(?=\s*:)/i,
-	'important': /\B!important\b/i,
+	'important': /!important\b/i,
 	'function': /[-a-z0-9]+(?=\()/i,
 	'punctuation': /[(){};:]/
 };
@@ -889,4 +889,4 @@ Prism.languages.js = Prism.languages.javascript;
 
 	document.addEventListener('DOMContentLoaded', self.Prism.fileHighlight);
 
-})();
+})();

tests/languages/css/important_feature.test

@@ -1,5 +1,6 @@
 color: red !important;
 padding: 10px 20px 30px !important;
+position:absolute!important;
 
 ----------------------------------------------------
 
@@ -10,12 +11,17 @@ padding: 10px 20px 30px !important;
 	["important", "!important"],
 	["punctuation", ";"],
 	["property", "padding"],
-    ["punctuation", ":"],
-    " 10px 20px 30px ",
-    ["important", "!important"],
-    ["punctuation", ";"]
+	["punctuation", ":"],
+	" 10px 20px 30px ",
+	["important", "!important"],
+	["punctuation", ";"],
+	["property", "position"],
+	["punctuation", ":"],
+	"absolute",
+	["important", "!important"],
+	["punctuation", ";"]
 ]
 
 ----------------------------------------------------
 
-Checks for !important rule.
+Checks for !important rule.