Change relaxed-autolinks to allow any url scheme

[digitalmoksha]

This change makes the relaxed-autolinks option allow any url scheme to be detected.

For example, smb://example.com would be detected as an autolink.

Closes #379

[github-actions]

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
./bench.sh ./comrak-3bafd47	320.2 ± 1.1	318.5	323.1	2.88 ± 0.02
./bench.sh ./comrak-main	321.1 ± 5.4	317.8	344.4	2.89 ± 0.05
./bench.sh ./pulldown-cmark	111.3 ± 0.5	110.3	112.3	1.00
./bench.sh ./cmark-gfm	118.8 ± 0.8	116.9	120.6	1.07 ± 0.01
./bench.sh ./markdown-it	479.3 ± 5.8	472.9	493.9	4.31 ± 0.06

Run on Wed Apr 24 22:35:57 UTC 2024

[kivikakk]

I've had a think about and a play with this — all LGTM. Thank you!