* Changes `make_channel!` macro to accept more types
Changes `type` macro argument from `path` to `ty`, allowing more complex
types like tuples, arrays, & pointers.
See https://doc.rust-lang.org/reference/types.html#type-expressions.
* Adds to `CHANGELOG.md`
Before, `make_channel` assumed that `critical_section` would be
available in the namespace of the code that invoked the macro. Access
`critical_section` through `rtic-sync` instead.