Add fallback for upstream version fetching

[zekroTJA]

Currently, the upstream version fetching relies on the git ls-remote command. There should be a fallback in place when git is not available on the system which queries tags via the GitHub Rest API.

[zekroTJA]

Well, fetching the list of tags via the REST API is actually way faster than using git ls-remote --tags. So, the default behavior will be the REST API request and git ls-remote --tags will be used as fallback if the API request fails.

Here you can see the results of benchmarking goup lsr using hyperfine with 3 warmup runs and 20 benchmark runs.

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
lsr (git ls-remote --tags)	372.5 ± 25.8	345.9	469.2	1.00
lsr (GitHub API)	73.9 ± 77.3	38.3	335.3	1.00
lsr (GitHub API + git fallback)	71.9 ± 70.5	38.6	292.3	1.00