* final draft of proposal
* fix alloc formal
* resolve ambiguity and fix TODO
* some wording improvements
* apply some feedback after offline review w/ @GabrielDosReis
* Update specification after review from C++ Core Guidelines
- Make sure iterators and references cannot be invalidated by any
operations (besides destruction).
- Update specification to annotate that some functions require certain
language features (ranges and concepts).
- Remove dependence on "Container" named requirements because they
require iterator-invalidating behavior.
- Explicitly add default and move constructors.
- Fix some typos
* Update dyn_array documentation reflecting editors' feedback
Clarified that `gsl::dyn_array` cannot be moved or copied. Updated the FAQ section to emphasize that it is a fixed-size array without iterator/pointer-invalidating operations.
* Update FAQ regarding gsl::dyn_array usage
Clarified the purpose of gsl::dyn_array in the FAQ section.
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Co-authored-by: Gabriel Dos Reis <GabrielDosReis@users.noreply.github.com>
