Add README description of the new window.PlotlyConfig.MathJaxConfig property

Author: jonmmease

dist/README.md

@@ -33,6 +33,19 @@ or the un-minified version as:
 
 You can grab the relevant MathJax files in `./dist/extras/mathjax/`.
 
+By default, plotly.js will modify the global MathJax configuration on load.
+This can lead to undesirable behavior if plotly.js is loaded alongside
+other libraries that also rely on MathJax. To disable this global configuration
+process, set the `MathJaxConfig` property to `'local'` in the `window.PlotlyConfig`
+object.  This property must be set before the plotly.js script tag, for example:
+
+```html
+<script>
+    window.PlotlyConfig = {MathJaxConfig: 'local'}
+</script>
+<script src="plotly.min.js"></script>
+```
+
 ### To include localization
 
 Plotly.js defaults to US English (en-US) and includes British English (en) in the standard bundle.