Update heapless requirement from 0.7 to 0.8

Updates the requirements on [heapless](https://github.com/rust-embedded/heapless) to permit the latest version.
- [Changelog](https://github.com/rust-embedded/heapless/blob/main/CHANGELOG.md)
- [Commits](rust-embedded/heapless@v0.7.0...v0.7.16)

---
updated-dependencies:
- dependency-name: heapless
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-Authored-By: Ralph Ursprung <[email protected]>

Author: dependabot[bot]

CHANGELOG.md

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased] - ReleaseDate
 ### Changed
 * Due to dependency updates the MSRV has been updated from 1.60 to 1.62. This should only be relevant if you use the `defmt` feature, but we now only test with 1.62 and not older releases, so it's not guaranteed to work otherwise.
+* Update to `heapless:0.8.0`
 
 ## [0.1.1] - 2023-01-07
 ### Changed

Cargo.toml

@@ -12,15 +12,15 @@ license = "MIT OR Apache-2.0"
 
 [dependencies]
 defmt = { version = "0.3", optional = true }
-heapless = { version = "0.7" }
+heapless = { version = "0.8" }
 
 rgb = { version = "0.8", optional = true }
 serde = { version = "1.0", features = ["derive"], optional = true }
 
 [features]
 default = ["accelerometer_event", "button_event", "color_event", "gyro_event", "location_event", "magnetometer_event", "quaternion_event"]
 
-defmt = ["dep:defmt", "heapless/defmt-impl"]
+defmt = ["dep:defmt", "heapless/defmt-03"]
 
 accelerometer_event = []
 button_event = []