Prepare changelog for v0.6.4-rc.1
Prepare changelog for v0.6.4-rc.1

williamboman/matrix-js-sdk,williamboman/matrix-js-sdk,matrix-org/matrix-js-sdk,krombel/matrix-js-sdk,krombel/matrix-js-sdk,matrix-org/matrix-js-sdk,krombel/matrix-js-sdk,williamboman/matrix-js-sdk,matrix-org/matrix-js-sdk,matrix-org/matrix-js-sdk