Auto detect latest release if "latest" is used

[GuybrushX]

Should fix #1

[sandrich]

Thanks @GuybrushX for the contribution. I have adde a comment inline. I think we should not use jq has the majority does not have it installed. Rather use sed or awk

[GuybrushX]

Quick research on using sed or awk to parse JSON seems to be pretty hacky.

What do you think about using Python instead?

Here are some examples, also using the GitHub API so I think it should work - just have to fiddle around with Python:
https://stackoverflow.com/questions/1955505/parsing-json-with-unix-tools

Is it safe to assume that Python 3 is installed?

[sandrich]

I think python is even worse I have already found some system without curl installed :D let me think about it

[sandrich]

This could be a version of it

curl -s "https://api.github.com/repos/DeFiCh/ain/releases/latest" | grep tag_name | sed -r 's/.*"v(.*)",$/\1/g'

There are some installations without curl. We probably need to check if curl is installed