Add compatibility with Chrome (#1)

* Add compatibility with Chrome
* Upgrade packages and fix icons

Author: beckbria

addon/icons/aoc-to-markdown-128.png

@@ -4,10 +4,18 @@
     "version": "1.0.3",
     "description": "Converts a given Advent of Code page to a GitHub-compatible Markdown file.",
     "icons": {
-        "32": "icons/aoc-to-markdown.svg"
+        "16": "icons/aoc-to-markdown-16.png",
+        "32": "icons/aoc-to-markdown-32.png",
+        "48": "icons/aoc-to-markdown-48.png",
+        "128": "icons/aoc-to-markdown-128.png"
     },
     "page_action": {
-        "default_icon": "icons/aoc-to-markdown.svg",
+        "default_icon": {
+            "16": "icons/aoc-to-markdown-16.png",
+            "32": "icons/aoc-to-markdown-32.png",
+            "48": "icons/aoc-to-markdown-48.png",
+            "128": "icons/aoc-to-markdown-128.png"
+        },
         "default_title": "Advent of Code to Markdown"
     },
     "background": {

addon/icons/aoc-to-markdown-16.png

@@ -1,3 +1,5 @@
+const browser = require("webextension-polyfill");
+
 function urlIsApplicable(url) {
     const regex = /^https:\/\/adventofcode.com\/\d{4}\/day\/\d{1,2}/;
     return regex.test(url);

addon/icons/aoc-to-markdown-32.png

@@ -1,3 +1,4 @@
+const browser = require("webextension-polyfill");
 const gfm = require('turndown-plugin-gfm').gfm;
 const TurndownService = require('turndown').default;