add documenting in MDN as a step in browser bug handling process

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CONTRIBUTING.md

@@ -98,7 +98,7 @@ Example:
 ### Reporting upstream browser bugs
 
 Sometimes bugs reported to us are actually caused by bugs in the browser(s) themselves, not bugs in Bootstrap per se.
-When feasible, we aim to report such upstream bugs to the relevant browser vendor(s), and then list them on our [Wall of Browser Bugs](http://getbootstrap.com/browser-bugs/).
+When feasible, we aim to report such upstream bugs to the relevant browser vendor(s), and then list them on our [Wall of Browser Bugs](http://getbootstrap.com/browser-bugs/) and [document them in MDN](https://developer.mozilla.org/en-US/docs/Web).
 
 | Vendor(s)     | Browser(s)                   | Rendering engine | Bug reporting website(s)                                                              | Notes                                                    |
 | ------------- | ---------------------------- | ---------------- | ------------------------------------------------------------------------------------- | -------------------------------------------------------- |