Git commits in Moodle 3.9.0 by David Thompson

commit 5bc86614a2dface8ed31ad2f2449478c15616aa2
Author: David Thompson <david.thompson@catalyst.net.nz>
Date:   Tue, 21 Apr 2020 04:48:39 +0800
Tag:    v3.9.0-beta

MDL-68477 libraries: support for Chart.js legend options.

commit ab0d4099915fc96980144635a6365ca6cd414238
Author: David Thompson <david.thompson@catalyst.net.nz>
Date:   Thu, 09 Apr 2020 09:14:31 +0800
Tag:    v3.9.0-beta

MDL-68386 libraries: Enhancement for Area Charts support with chart.js.