support GitHub pre-release tags

[jmbarbone]

In case someone wants to use the most recent pre-release (at their own risk), something like github::owner/repo/@*pre-release would be helpful.

The release tag type is at least easily visible with the gh cli.

$ gh release list
TITLE           TYPE         TAG NAME     PUBLISHED
fuj 0.2.1.9007  Pre-release  v0.2.1.9007  about 1 month ago
fuj 0.2.1.9006  Pre-release  v0.2.1.9006  about 1 month ago
fuj 0.2.1.9005  Pre-release  v0.2.1.9005  about 1 month ago
fuj 0.2.1.9003  Pre-release  v0.2.1.9003  about 5 months ago
fuj 0.2.1.9001  Pre-release  v0.2.1.9001  about 8 months ago
fuj 0.2.1       Latest       v0.2.1       about 9 months ago
fuj 0.2.0                    v0.2.0       about 10 months ago
fuj 0.1.4.9011  Pre-release  v0.1.4.9011  about 10 months ago
fuj 0.1.4.9010  Pre-release  v0.1.4.9010  about 11 months ago
fuj 0.1.4.9009  Pre-release  v0.1.4.9009  about 1 year ago
fuj 0.1.4.9008  Pre-release  v0.1.4.9008  about 1 year ago
fuj 0.1.4.9007  Pre-release  v0.1.4.9007  about 1 year ago
fuj 0.1.4                    v0.1.4       about 1 year ago
fuj 0.1.3                    v0.1.3       about 1 year ago
fuj 0.1.2                    v0.1.2       about 2 years ago
fuj 0.1.1                    v0.1.1       about 2 years ago
fuj 0.1.0                    v0.1.0       about 2 years ago