chore: Add .gitignore file

[ctruta]

Inspired by GitHub's gitignore project; adapted from libpng and optipng.
See https://github.com/github/gitignore

[ctruta]

@ronaldtse, following up on my comments in PR #52, please review.
@svgeesus, @jbowler: ditto. Hope this is satisfactory to your development workflows as it is to mine.

[ronaldtse]

@ctruta LTGM!

GitHub also has a CMake gitignore template, you probably already saw it.

If the team is going for "CMake handles the Makefile", then one day Makefile should also appear here 😉

[ctruta]

@ctruta LTGM!

Thank you.

GitHub also has a CMake gitignore template, you probably already saw it.

Yes, but the only artifact I picked from there is CMakeUserPresets.json, as recommended in the CMake presets documentation:

CMakePresets.json may be checked into a version control system, and CMakeUserPresets.json should NOT be checked in. For example, if a project is using Git, CMakePresets.json may be tracked, and CMakeUserPresets.json should be added to the .gitignore.

The other ones are for in-tree builds, which are semi-supported and not officially recommended. I mean, considering your original patch, adding the build/ directory to .gitignore -- all CMake users should be doing that, at the very least!

If the team is going for "CMake handles the Makefile", then one day Makefile should also appear here 😉

Ha! I sincerely doubt that the traditional users of traditional Make are going to like a big giant CMake artifact replacing our small and simple and neat Makefile. After all, I kept our plain Unix Makefile in there for a good reason. But of course, I always can be (and oftentimes am) proven wrong 😄