Add .gitattributes for GitHub Linguist

[formatc1702]

This is an attempt to use GitHub Linguist to

• avoid the examples/ and tutorial/ directories to be included in the project's language statistics
• mark any WireViz output files (TSV, CSV, GV, HTML, SVG, PNG) as generated files

Unfortunately, it seems that the statistics are only updated when merged into master, so maybe someone with more experience can confirm that my implemenation will actually have the intended effect.

[formatc1702]

Coming in #111

[kvid]

I accidentally deleted this part of my review 10 hours ago, but I've tried to reconstruct it here:
We don't strictly need an override for the docs/ or example/ directories as they seem to be covered by documentation.yml already, but I agree to keep them anyway to state the fact explicitly. I tested by renaming tutorial/ to docs/:

[formatc1702]

Does it make sene to move examples/ and tutorial/ into the docs/ directory?

[kvid]

A tutorial and examples are definitely important parts of the documentation, but moving them into the docs/ directory or not is perhaps a matter of taste. Some might argue that it might be less easy to discover them if moving them, and others might argue that they always start with the docs/ anyway and don't see a problem. If moving them, please include links to them both from the root README.md and from the docs/README.md.

We don't strictly need an override for the tutorial/ directory either, probably because the of the **/*.html linguist-generated further down in this file, but I agree to keep them anyway to state the fact explicitly. However, I suggest using linguist-documentation in both of them. I tested without any directory overrides:

[kvid]

This is an attempt to use GitHub Linguist to

• avoid the examples/ and tutorial/ directories to be included in the project's language statistics
• mark any WireViz output files (TSV, CSV, GV, HTML, SVG, PNG) as generated files

Unfortunately, it seems that the statistics are only updated when merged into master, so maybe someone with more experience can confirm that my implemenation will actually have the intended effect.

I didn't have any experience with the language statistics either, so I did some tests in my forked repo:

1. First, I had to force-push your master into my fork master to have the same starting point as you. (I originally forked from aakatz3 which had a master not in sync with your master.)
2. Then I cherry-picked your single commit in this PR into my master and pushed that to my fork:

git cherry-pick aedd53393ca2052f2b8dc5f87d54b2a0ef510a94
git push kvid

Before the cherry-pick, the language statistics looked identical to yours:

After pushing the cherry-picked commit, the language statistics changed:

If this was the result you aimed for, then I conclude that you should consider including this PR in v0.2. I only have the very minor change suggestion about replacing -linguist-detectable with linguist-documentation to state that it is documentation, but it's not very important to me because the effect is the same.

[kvid]

A tutorial and examples are definitely important parts of the documentation, but moving them into the docs/ directory or not is perhaps a matter of taste. Some might argue that it might be less easy to discover them if moving them, and others might argue that they always start with the docs/ anyway and don't see a problem. If moving them, please include links to them both from the root README.md and from the docs/README.md.

We don't strictly need an override for the tutorial/ directory either, probably because the of the **/*.html linguist-generated further down in this file, but I agree to keep them anyway to state the fact explicitly. However, I suggest using linguist-documentation in both of them. I tested without any directory overrides:

[formatc1702]

Thank you very much for running this test. I've changed -linguist-detectable to linguist-documentation as suggested.
Moving examples and tutorial into docs/ can happen later. :)