Version 1.4.0

"1.4.0" (https://github.com/gainzgg/gainz.gg/compare/v1.3.0...v1.4.0) (2021-07-08): Features: playlist: support solo and quad buy backs ("c7b9ea8" (https://github.com/gainzgg/gainz.gg/commit/c7b9ea8ee770d7f12b7c37fcdc8d95e63c0f6860))