Bump version to 0.5.0

[awvwgk]

Test release at https://github.com/awvwgk/fortran-package-manager/releases/tag/v0.5.0

Tentative release notes:

Alpha release update for the Fortran package manager (fpm).

**Changes**

- tests are only build for fpm test and not by default anymore (https://github.com/fortran-lang/fpm/pull/572)

- environment variables for setting Fortran and C compiler changed (https://github.com/fortran-lang/fpm/pull/549, https://github.com/fortran-lang/fpm/pull/584)

- add LFortran optimization flag to release profile (https://github.com/fortran-lang/fpm/pull/597) 


**New features**

- command line arguments for linker, archiver and C-compiler added (https://github.com/fortran-lang/fpm/pull/549)


**Fixes**

- tabs are correctly expanded in source file scanning (https://github.com/fortran-lang/fpm/pull/521)

- installer script will use fpm update to avoid stale dependencies (https://github.com/fortran-lang/fpm/pull/557)

- use multiple build output directories depending on link line options (https://github.com/fortran-lang/fpm/pull/575)

- update truncated help text (https://github.com/fortran-lang/fpm/pull/578)

- fix directory removal in fpm new tests (https://github.com/fortran-lang/fpm/pull/579)

- use MSVS like commands for Intel compilers on Windows (https://github.com/fortran-lang/fpm/pull/590)

- add critical section to mkdir in backend (https://github.com/fortran-lang/fpm/pull/613)

- fix modules listing (for install) (https://github.com/fortran-lang/fpm/pull/612)

- repair --list option and correct obsolete descriptions of the --list option (https://github.com/fortran-lang/fpm/pull/607)

- fix incorrect Intel release flag on Windows (https://github.com/fortran-lang/fpm/pull/602)

- list names without suffix for Windows (https://github.com/fortran-lang/fpm/pull/595)


**Repository updates**

- add files and workflow to make installer on release (https://github.com/fortran-lang/fpm/pull/616)

- issue templates added to guide reporting of bugs, package issues, feature requests and specification proposals (https://github.com/fortran-lang/fpm/pull/558)

- default branch renamed to *main* (https://github.com/fortran-lang/fpm/pull/565)

- update documentation on distributions supporting fpm, like spack and MSYS2 (https://github.com/fortran-lang/fpm/pull/562)

- new workflow to automatically generate single source fpm versions (https://github.com/fortran-lang/fpm/pull/563)

- continuous delivery of current fpm git source implemented (https://github.com/fortran-lang/fpm/pull/564, https://github.com/fortran-lang/fpm/pull/569)

- update of bootstrapping instructions (https://github.com/fortran-lang/fpm/pull/587)

- update README.md compiler, archiver, & link flags (https://github.com/fortran-lang/fpm/pull/598)

[ghost]

@awvwgk looks good.

[LKedward]

Cheers! LGTM 👍

[awvwgk]

Alright, I'll go ahead and make the release.