2020.06: Add slides for String#replaceAll

Note that these are not new materials; it's just an easier overview of information that's already in the repository.

2020/06.md

@@ -76,7 +76,7 @@ Supporting materials includes slides, a link to the proposal repository, a link
 
     | ✓ | stage | timebox | topic | presenter |
     |:-:|:-----:|:-------:|-------|-----------|
-    |   | 3     | 15m     | [`String.prototype.replaceAll`](https://github.com/tc39/proposal-string-replace-all) for Stage 4 (slides TBD) | Mathias Bynens |
+    |   | 3     | 15m     | [`String.prototype.replaceAll`](https://github.com/tc39/proposal-string-replace-all) for Stage 4 ([slides](https://docs.google.com/presentation/d/143RkssdqvENZIKCpZVGaHYC5JaIm4mJIdHdTor58IMQ/edit)) | Mathias Bynens |
     |   | 3     | 15m     | Logical Assignment ([Status Update][lgcl-assign], [NamedEvaluation][lgcl-namedevaluation]) | Justin Ridgewell |
     |   | 3     | 15m     | Changing Promise.any's AggregateError's argument processing order ([PR](https://github.com/tc39/proposal-promise-any/pull/59)) | Shu-yu Guo |
     |   | 2     | 5m      | [Decorators](https://github.com/tc39/proposal-decorators/) status update | Chris Garrett |