### Tasks
- [x] create v4 release branch
- [ ] https://github.com/adopted-ember-addons/ember-launch-darkly/pull/486
- [ ] https://github.com/adopted-ember-addons/ember-launch-darkly/pull/498
- [ ] verify which other dependencies drop 3.28 support that can be merged
- [ ] Remove 3.28 from ember try scenarios
- [ ] Update readme
This will remove support for Ember 3.28 as it's a long outdated LTS. I created a branch https://github.com/adopted-ember-addons/ember-launch-darkly/tree/v4-release to be used for beta releases.