- Refactoring: Reorder path config to group (non-modular-dependent) image

paths together (and correct code comment)
- Docs: CHANGES clarifications/fixes
- Docs: Migrations documents section
- Docs: Add code comment re: use of `extIconsPath` in Mathjax
- Docs: Add JSDoc indicate @this for `ExtensionInitResponse#callback`
- Build: Update build files
- npm: Bump to 3.1.0

editor/extensions/ext-mathjax.js

@@ -189,6 +189,8 @@ export default {
               svgEditor.curConfig.extIconsPath + mathjaxSrcSecure
             );
             */
+            // We use `extIconsPath` here for now as it does not vary with
+            //  the modular type as does `extPath`
             importScript(svgEditor.curConfig.extIconsPath + mathjaxSrcSecure).then(() => {
               // When MathJax is loaded get the div where the math will be rendered.
               MathJax.Hub.queue.Push(function () {