Options: use MD icons in the language editor buttons

This unifies how the buttons look in different OSs, because before we
relied in the characters being rendered by the default sans-serif font
installed in the computer.

Bug: translateselectedtext:12
Change-Id: I70e524f9664a957637f37e81465c9ec435ecc3dd
diff --git a/package-lock.json b/package-lock.json
index 4aaae85..0d4cec1 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -9,6 +9,7 @@
       "version": "0.0.0",
       "license": "MIT",
       "dependencies": {
+        "@mdi/js": "^6.7.96",
         "@polymer/paper-button": "^3.0.1",
         "chrome-types": "^0.1.113",
         "clean-terminal-webpack-plugin": "^3.0.0",
@@ -83,6 +84,11 @@
       "resolved": "https://registry.npmjs.org/@lit/reactive-element/-/reactive-element-1.3.2.tgz",
       "integrity": "sha512-A2e18XzPMrIh35nhIdE4uoqRzoIpEU5vZYuQN4S3Ee1zkGdYC27DP12pewbw/RLgPHzaE4kx/YqxMzebOpm0dA=="
     },
+    "node_modules/@mdi/js": {
+      "version": "6.7.96",
+      "resolved": "https://registry.npmjs.org/@mdi/js/-/js-6.7.96.tgz",
+      "integrity": "sha512-vZvhFrNN9LQx+Awu3nU6ESfXXDpRA/CA4mwikzU5g8uf9NpAocK43ecQvVNntwiXlLKpyplas8d4lsfpqjtXLA=="
+    },
     "node_modules/@nodelib/fs.scandir": {
       "version": "2.1.5",
       "resolved": "https://registry.npmjs.org/@nodelib/fs.scandir/-/fs.scandir-2.1.5.tgz",
@@ -3159,6 +3165,11 @@
       "resolved": "https://registry.npmjs.org/@lit/reactive-element/-/reactive-element-1.3.2.tgz",
       "integrity": "sha512-A2e18XzPMrIh35nhIdE4uoqRzoIpEU5vZYuQN4S3Ee1zkGdYC27DP12pewbw/RLgPHzaE4kx/YqxMzebOpm0dA=="
     },
+    "@mdi/js": {
+      "version": "6.7.96",
+      "resolved": "https://registry.npmjs.org/@mdi/js/-/js-6.7.96.tgz",
+      "integrity": "sha512-vZvhFrNN9LQx+Awu3nU6ESfXXDpRA/CA4mwikzU5g8uf9NpAocK43ecQvVNntwiXlLKpyplas8d4lsfpqjtXLA=="
+    },
     "@nodelib/fs.scandir": {
       "version": "2.1.5",
       "resolved": "https://registry.npmjs.org/@nodelib/fs.scandir/-/fs.scandir-2.1.5.tgz",