Add the ability to open a file from a specific commit (complement of #674)

[Cyrillev91]

Hi,

complement of #674 :

Is it possible that the "Open With ..." function opens the commit file and not the working directory file.
The steps performed by the SourceGit software would be:

• creation of the file (like the Save As of the same menu) but in a temporary folder of the system
• opening of the temporary file with default software (like the current Open With)

The name of the temporary file could be name~sha1.ext

example to open the file README.md from commit 67cf232
name of the temporary file: README~67cf23267.md

[love-linger]

Done. You can download the latest CI build from Github Actions

[Cyrillev91]

Thanks a lot