LGTM.com-inspired changes:

- Fix: Ensure all apostrophes are escaped for `toXml` utility
- Fix: Avoid error if `URL` is not defined
- Fix (jPicker): Precision argument had not been passed in previously
- Fix (Star extension): Minor: Avoid erring if `inradius` is `NaN`
- Refactoring: Avoid passing unused arguments, setting unused variables,
  and making unnecessary checks; avoid useless call to `createSVGMatrix`
- Linting (LGTM): Add `lgtm.yml` file (still some remaining items flagged
  but hoping for in-code flagging)
- Docs: Contributing file

editor/canvg/canvg.js

@@ -168,9 +168,6 @@ function build (opts) {
     const AJAX = window.XMLHttpRequest
       ? new XMLHttpRequest()
       : new window.ActiveXObject('Microsoft.XMLHTTP');
-    if (!AJAX) {
-      return null;
-    }
     if (asynch) {
       return new Promise((resolve, reject) => {
         const req = AJAX.open('GET', url, true);