(INCOMPLETE: ES6 Module conversion and linting)

- Breaking change: Require `new` with `EmbeddedSVGEdit` (allows us to use `class` internally)
- Breaking change: If `svgcanvas.setUiStrings` must now be called if not using editor in order
    to get strings (for sake of i18n) (and if using path.js alone, must also have its `setUiStrings` called)
- Breaking change (ext-overview-window): Avoid global `overviewWindowGlobals`
- Breaking change (ext-imagelib): Change to object-based encoding for namespacing of
    messages (though keep stringifying/parsing ourselves until we remove IE9 support)
- Breaking change: Rename `jquery.js` to `jquery.min.js`
- Breaking change: Remove `scoped` attribute from `style`; it is now deprecated and
    obsolete; also move to head (after other stylesheets)
- Enhancement: Make SpinButton plugin independent of SVGEdit via
    generic state object for tool_scale
- Enhancement: Remove now unused Python l10n scripts (#238)
- Enhancement: ES6 Modules (including jQuery plugins but not jQuery)
- Enhancement: Further JSDoc (incomplete)
- Enhancement (Optimization): Compress images using imageoptim (and add
    npm script) (per #215)
- Fix: i18nize path.js strings and canvas notifications
- Fix: Attempt i18n for ext-markers
- Refactoring (ext-storage): Move locale info to own file imported by the extension (toward modularity; still should be split into separate files by language and *dynamically* imported, but we'll wait for better `import` support to refactor this)
- Refactoring: For imagelib, add local jQuery copy (using old 1.4.4 as had
    been using from server)
- Refactoring: For MathJax, add local copy (using old 2.3 as had been using from
    server); server had not been working
- Refactoring: Remove `use strict` (implicit in modules)
- Refactoring: Remove trailing whitespace, fix some code within comments
- Refactoring: Expect `jQuery` global rather than `$` for better modularity
    (also to adapt line later once available via `import`)
- Refactoring: Prefer `const` (and then `let`)
- Refactoring: Add block scope keywords closer to first block in which they appear
- Refactoring: Use ES6 `class`
- Refactoring `$.isArray` -> `Array.isArray` and avoid some other jQuery core methods
    with simple VanillaJS replacements
- Refactoring: Use abbreviated object property syntax
- Refactoring: Object destructuring
- Refactoring: Remove `uiStrings` contents in svg-editor.js (obtains from locale)
- Refactoring: Add favicon to embedded API file
- Refactoring: Use arrow functions for brief functions (incomplete)
- Refactoring: Use `Array.prototype.includes`/`String.prototype.includes`;
    `String.prototype.startsWith`, `String.prototype.trim`
- Refactoring: Remove now unnecessary svgutils do/while resetting of variables
- Refactoring: Use shorthand methods for object literals (avoid ": function")
- Refactoring: Avoid quoting object property keys where unnecessary
- Refactoring: Just do truthy/falsey check for lengths in place of comparison to 0
- Refactoring (Testing): Avoid jQuery usage within most test files (defer script,
    also in preparation for future switch to ES6 modules for tests)
- Refactoring: Make jpicker variable declaration indent bearable
- Refactoring (Linting): Finish svgcanvas.js
- Docs: Mention in comment no longer an entry file as before
- Docs: Migrate old config, extensions, and FAQ docs
- Licensing: Indicate MIT is license type of rgbcolor; rename/add license file name for
    jgraduate and screencast to reflect type (Apache 2.0); rename file to reflect it
    contains license information (of type MIT) for Raphael icons

editor/extensions/ext-webappfind.js

@@ -1,4 +1,3 @@
-/* eslint-disable no-var */
 /* globals svgEditor */
 /*
 Depends on Firefox add-on and executables from https://github.com/brettz9/webappfind
@@ -7,21 +6,20 @@ Todos:
 1. See WebAppFind Readme for SVG-related todos
 */
 (function () {
-'use strict';
-
-var pathID,
-  saveMessage = 'webapp-save',
+const saveMessage = 'webapp-save',
   readMessage = 'webapp-read',
   excludedMessages = [readMessage, saveMessage];
+let pathID;
 
+// Todo: Update to new API once released
 window.addEventListener('message', function (e) {
   if (e.origin !== window.location.origin || // PRIVACY AND SECURITY! (for viewing and saving, respectively)
-    (!Array.isArray(e.data) || excludedMessages.indexOf(e.data[0]) > -1) // Validate format and avoid our post below
+    (!Array.isArray(e.data) || excludedMessages.includes(e.data[0])) // Validate format and avoid our post below
   ) {
     return;
   }
-  var svgString,
-    messageType = e.data[0];
+  const messageType = e.data[0];
+  let svgString;
   switch (messageType) {
   case 'webapp-view':
     // Populate the contents
@@ -54,7 +52,7 @@ svgEditor.addExtension('WebAppFind', function () {
       title: 'Save Image back to Disk',
       position: 4, // Before 0-based index position 4 (after the regular "Save Image (S)")
       events: {
-        click: function () {
+        click () {
           if (!pathID) { // Not ready yet as haven't received first payload
             return;
           }