Fix the readme’s first link to benchmarks

[acusti]

for some reason, the faster link at the top of the README in the description block gets interpreted as pointing to github.com/bench. making it a fully relative link (no leading slash) fixes that issue.

here’s a link to the readme file showing the bad link URL resolution on master: https://github.com/lukeed/clsx/blob/master/readme.md

and here’s a link to the readme file in the same GitHub view but from this branch: https://github.com/acusti/clsx/blob/patch-1/readme.md

oh yes, and thank you so much for this package! it’s such a wonderful asset for the community.

[lukeed]

Oh bummer. This might have been an unintended change in the last batch of GH readme updates

thanks for this