sr.ht/py3-scmsrht: upgrade to 0.18.1

py3-srht, py3-scmsrht: update checksums

Update py3-srht & py3-scmsrht

Add builds.sr.ht as scm.sr.ht dependency

Fix archive URL for scm.sr.ht package

Add py3-scmsrht package, update py3-srht