Remove linkid stripping

This token name is rather generic and is used by some sites in a
non-tracking context. Rather than complicate the logic with exceptions,
I think the best solution is to simply take no action for this token.

Closes #46

README.md

@@ -16,7 +16,6 @@ The following query string parameters are stripped:
   - `fbclid`
 - Google
   - `gclid`
-  - `linkid`
   - `utm_source`
   - `utm_medium`
   - `utm_term`

background.js

@@ -3,15 +3,15 @@
  * parameter. We'll search the query string portion of the URL for this
  * pattern to determine if there's any stripping work to do.
  */
-const searchPattern = new RegExp('utm_|stm_|clid|_hs|icid|igshid|linkid|mc_|mkt_tok|yclid|_openstat|wicked|otc|oly_|rb_clickid|soc_', 'i');
+const searchPattern = new RegExp('utm_|stm_|clid|_hs|icid|igshid|mc_|mkt_tok|yclid|_openstat|wicked|otc|oly_|rb_clickid|soc_', 'i');
 
 /*
  * Pattern matching the query string parameters (key=value) that will be
  * stripped from the final URL.
  */
 const replacePattern = new RegExp(
     '([?&]' +
-    '(icid|mkt_tok|(g|fb)clid|igshid|_hs(enc|mi)|linkid|mc_[ce]id|(utm|stm)_(source|medium|term|campaign|content|cid|reader|referrer|name|social|social-type)|rb_clickid|yclid|_openstat|wickedid|otc|oly_(anon|enc)_id|soc_(src|trk))' +
+    '(icid|mkt_tok|(g|fb)clid|igshid|_hs(enc|mi)|mc_[ce]id|(utm|stm)_(source|medium|term|campaign|content|cid|reader|referrer|name|social|social-type)|rb_clickid|yclid|_openstat|wickedid|otc|oly_(anon|enc)_id|soc_(src|trk))' +
     '=[^&#]*)',
     'ig');
 

manifest.json

@@ -1,6 +1,6 @@
 {
 	"name": "Tracking Token Stripper",
-	"version": "2.8",
+	"version": "2.9",
 	"manifest_version": 2,
 	"author": "Jon Parise",
 	"description": "Removes Google Analytics (UTM) parameters, and various other click tracking tokens, from URL query strings.",