Make altitude component of GpsInfo optional

Clean up some uses of unwrap() and replace them with ?

Do not reduce/simplify rational values (i.e. 16/10 is not 8/5)

Version 0.10.0

Metadata::get_tag_rational(): avoid panic if denominator is 0

Support Windows paths by assuming UTF-8 everywhere

New API: Metadata::new_from_app1_segment

Bump dependency versions of gexiv2-sys and glib-sys

Improve doc examples/tests

Improve test coverage

Add Makefile for common dev tasks

Set up test code coverage reporting as part of CI

Make Clippy a bit more thorough

Add REUSE/SPDX licensing/software BOM metadata

Set up linting and format checking in CI