feat: add use_extendr_badge()

[JosiahParry]

Currently in draft status.

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 82.90%. Comparing base (88ec630) to head (9bd0985).

Files with missing lines	Patch %	Lines
R/badge.R	85.71%	2 Missing ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
R/use_extendr.R	98.95% <100.00%> (+0.01%)	⬆️
R/badge.R	85.71% <85.71%> (ø)

... and 1 file with indirect coverage changes

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[Ilia-Kosenkov]

I realized I did not actually comment here, but created a pending review comment 🤦 .

[Ilia-Kosenkov]

Why do you use it by default?

[JosiahParry]

Ah, as a point of encouragement. It does quite literally nothing other than print a message to the console. The hope is that users can add it to their package for a bit of flair and provide and indication that they're R package is rust powered.

[Ilia-Kosenkov]

It feels like it defeats the purpose, a user still have to run use_extendr() once. What's the point of a separate function? Perhaps it is better to show here an invite to run rextendr::use_extendr_badge()?