chore: update changelog for 0.8.6

CHANGELOG.md

@@ -1,3 +1,11 @@
+## [0.8.6](https://github.com/opensheetmusicdisplay/opensheetmusicdisplay/compare/0.8.5...0.8.6)  (2020-09-15)
+
+### Bug Fixes
+* **Voltas, Tabs**: Fix regression in 0.8.5 where repetition volta shift and tabnote svg id were fixes were not applied (will soon be fixed by vexflow patch script)
+
+### Miscellaneous
+* **Build**: Build size down to 1.1MB again from mysterious 1.3MB increase in 0.8.5
+
 ## [0.8.5](https://github.com/opensheetmusicdisplay/opensheetmusicdisplay/compare/0.8.4...0.8.5) (2020-09-08)