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/svgtransformlist.js

@@ -125,7 +125,7 @@ export class SVGTransformList {
     // TODO: how do we capture the undo-ability in the changed transform list?
     this._update = function () {
       let tstr = '';
-      /* const concatMatrix = */ svgroot.createSVGMatrix();
+      // /* const concatMatrix = */ svgroot.createSVGMatrix();
       for (let i = 0; i < this.numberOfItems; ++i) {
         const xform = this._list.getItem(i);
         tstr += transformToString(xform) + ' ';