Add neutered replacement script for mixpanel

Related discussion:
- https://www.reddit.com/r/uBlockOrigin/comments/oicch9/

The new replacement script contains the smallest API
possible to resolve the reported case.

Please report instances where it's not sufficient to
unbreak a site, in which case I will extend the neutered
API to address these cases on an on-demand basis.

src/js/redirect-engine.js

@@ -109,6 +109,8 @@ const redirectableResources = new Map([
     [ 'ligatus_angular-tag.js', {
         alias: 'ligatus.com/*/angular-tag.js',
     } ],
+    [ 'mxpnl_mixpanel.js', {
+    } ],
     [ 'monkeybroker.js', {
         alias: 'd3pkae9owd2lcf.cloudfront.net/mb105.js',
     } ],

src/web_accessible_resources/mxpnl_mixpanel.js

@@ -0,0 +1,51 @@
+/*******************************************************************************
+
+    uBlock Origin - a browser extension to block requests.
+    Copyright (C) 2021-present Raymond Hill
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see {http://www.gnu.org/licenses/}.
+
+    Home: https://github.com/gorhill/uBlock
+*/
+
+(function() {
+    'use strict';
+    // https://developer.mixpanel.com/docs/javascript-full-api-reference
+    const mixpanel = {
+        get_distinct_id() {
+            return '';
+        },
+        init(t, cfg) {
+            if ( cfg instanceof Object === false ) { return; }
+            if ( 'loaded' in cfg === false ) { return; }
+            if ( cfg.loaded instanceof Function === false ) { return; }
+            cfg.loaded();
+        },
+        register() {
+        },
+        register_once() {
+        },
+        track() {
+            const cb = Array.from(arguments).pop();
+            if ( cb instanceof Function === false ) { return; }
+            cb();
+        },
+    };
+    const q = self.mixpanel && self.mixpanel._i || [];
+    self.mixpanel = mixpanel;
+    for ( const i of q ) {
+        if ( Array.isArray(i) === false ) { continue; }
+        mixpanel.init(...i);
+    }
+})();