Add version checker for UltraPlot

[cvanelteren]

This PR would introduce a version check to inform users if a newer version of the package is available.

[codecov]

Codecov Report

❌ Patch coverage is 96.96970% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
ultraplot/__init__.py	33.33%	1 Missing and 1 partial ⚠️

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[beckermr]

I find these kinds of features a bit spammy except for cases like package managers etc. I'd prefer the default to be False so this is off unless someone really wants it.

[cvanelteren]

Hmm ok I hear you. The uptick for the more recent versions is not as high as the previous ones. I thought nudging people to upgrade would be a good idea. We could leave it out and put it in the refs indeed; do agree that package managers should handle this. Will think about it a bit and otherwise close this.

[cvanelteren]

Turned the default to off and added some tests.