Add missing changelog snippets

changes/changelog.d/bandwidth-limitation.feature

+Add option to limit bandwidth usage by streaming transcoded music

changes/changelog.d/bottom-sheet.feature

+Improve player bottom sheet, in particular fling support

changes/changelog.d/coverart-withContext.enhancement

+Refactor CoverArt.withContext().

changes/changelog.d/landscape.bugfix

+Fix landscape view induced MainActivity leak.

changes/changelog.d/progress-bar-buffering.bugfix

+Fix buffering progress bar display

changes/changelog.d/too-many-receivers.bugfix

+Fix Too Many Receivers exception