Properly handle instances of #?# or #$# in picker

Related feedback:
- https://github.com/uBlockOrigin/uBlock-issues/issues/1363#issuecomment-734957406

src/js/epicker-ui.js

@@ -45,6 +45,8 @@ const svgOcean = svgRoot.children[0];
 const svgIslands = svgRoot.children[1];
 const NoPaths = 'M0 0';
 
+const reCosmeticAnchor = /^#[$?]?#/;
+
 const epickerId = (( ) => {
     const url = new URL(self.location.href);
     if ( url.searchParams.has('zap') ) {
@@ -144,7 +146,7 @@ const userFilterFromCandidate = function(filter) {
     const hn = vAPI.hostnameFromURI(docURL.href);
 
     // Cosmetic filter?
-    if ( filter.startsWith('##') ) {
+    if ( reCosmeticAnchor.test(filter) ) {
         return hn + filter;
     }
 
@@ -460,7 +462,7 @@ const onCandidateChanged = function() {
     vAPI.MessagingConnection.sendTo(epickerConnectionId, {
         what: 'dialogSetFilter',
         filter,
-        compiled: filter.startsWith('##')
+        compiled: reCosmeticAnchor.test(filter)
             ? staticFilteringParser.result.compiled
             : undefined,
     });
@@ -487,13 +489,13 @@ const onCreateClicked = function() {
             autoComment: true,
             filters: filter,
             docURL: docURL.href,
-            killCache: /^#[$?]?#/.test(candidate) === false,
+            killCache: reCosmeticAnchor.test(candidate) === false,
         });
     }
     vAPI.MessagingConnection.sendTo(epickerConnectionId, {
         what: 'dialogCreate',
         filter: candidate,
-        compiled: candidate.startsWith('##')
+        compiled: reCosmeticAnchor.test(candidate)
             ? staticFilteringParser.result.compiled
             : undefined,
     });

src/js/scriptlets/epicker.js

@@ -38,6 +38,8 @@ if ( pickerRoot !== null ) { return; }
 
 let pickerBootArgs;
 
+const reCosmeticAnchor = /^#[$?]?#/;
+
 const netFilterCandidates = [];
 const cosmeticFilterCandidates = [];
 
@@ -739,7 +741,7 @@ const filterToDOMInterface = (( ) => {
             return;
         }
         lastFilter = filter;
-        if ( filter.startsWith('##') === false ) {
+        if ( reCosmeticAnchor.test(filter) === false ) {
             lastResultset = fromNetworkFilter(filter);
             if ( previewing ) { apply(); }
             return lastResultset;
@@ -789,7 +791,7 @@ const filterToDOMInterface = (( ) => {
             return unapply();
         }
         if ( Array.isArray(lastResultset) === false ) { return; }
-        if ( permanent === false || lastFilter.startsWith('##') === false ) {
+        if ( permanent === false || reCosmeticAnchor.test(lastFilter) === false ) {
             return apply();
         }
         if ( vAPI.domFilterer instanceof Object === false ) { return; }