[Feature Request] Add support for Go 1.18

[ajatprabha]

Hi, I was trying out Go 1.18 when I figured that gomarkdoc currently doesn't work with Go 1.18 projects that use generics.

For some code that uses generics

type Set[T comparable] map[T]bool

gomarkdoc currently gives error with 1.18 projects

gomarkdoc: failed to parse package: generic/set.go:4:12: expected ']', found comparable (and 1 more errors)

Wondering if the support is planned after a stable 1.18 release. Not sure how much effort this would be, I'm hoping it'll just require updating some parsing dependency in gomarkdoc.

[ajatprabha]

I just realised I have been using an older version(v0.2.1), updating it to latest removed the error. Closing the issue!