Add missing documentation
Add missing tests for `MediaTrackSettings`
Wrap bare property names into new-type `MediaTrackProperty` for type-safety
Change Rust edition from 2021 to 2018, backfilling explicit imports of `std::iter::FromIterator`
Move `mod name` & `fn names()` in `crate::property` into `all` sub-module
Delete unnecessary collection code in favor of `Deref` & `DerefMut`
Add implementation of `MediaTrackSetting`, `MediaTrackSettings` & `MediaStreamSettings`