* Add `no_std` support

* Highlight future work

* Test all feature/version combinations

* Explicitly list examples and their required features

* Feature gate tests which require `std`

* Simplify feature testing using `cargo-hack`

Co-Authored-By: Juniper Tyree <[email protected]>

* Added `CHANGELOG` entry for `no_std` support

Compared against `cargo-semver-checks` to ensure all breaking changes are captured. Note that while I have listed this as a breaking change, it technically isn't, as the functionality is still available with default features enabled.

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Co-authored-by: Juniper Tyree <[email protected]>

* SpannedError: Store position start and position end in span

* Update CHANGELOG.md

Co-authored-by: Juniper Tyree <[email protected]>

* fix: SpannedError: fmt displays start and end of span if they differ

* fix: errant tests and formatting

* ci: Clean between Check/Clippy/Test

* test: Add helpers for Position and Span error checking, and use them in all unit tests that use non-trivial Spans

* fix: place unicode-segmentation and the Span::substring helpers behind an optional (non-default) feature, include substring Span checks in non-trivial integration tests

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Co-authored-by: Juniper Tyree <[email protected]>

* Try to fix non-exhaustive Number enum (again)

* Use compile_fail doctests

* Adjust docs for the Number::__NonExhaustive variant

* Add CHANGELOG entry

* Add file IO with Vec<T> example

* Update CHANGELOG.md (#573)