Fix regex to match HTTPS as well for getHostname

[ken-matsui]

Currently, GitHub has two types of URLs: one is SSH, another is HTTPS. The getHostname function seems not to support HTTPS URL; therefore, gh-poi panics due to no matches in case of using HTTPS URL.

⠋ Fetching pull requests... panic: runtime error: index out of range [1] with length 0

goroutine 1 [running]:
main.getHostname({0x1400017a000, 0x6f})
        /home/runner/work/gh-poi/gh-poi/poi.go:106 +0xc4
main.GetBranches({0x100dc2d18, 0x100ea22f0})
        /home/runner/work/gh-poi/gh-poi/poi.go:67 +0x5c
main.main()
        /home/runner/work/gh-poi/gh-poi/main.go:38 +0x278

This PR brings a new regex that matches also HTTPS. You can check it out on regex101.com.

• Previous implementation: https://regex101.com/r/7pJr9R/1
• This change: https://regex101.com/r/PmJR16/1

[ken-matsui]

@seachicken Would you like me to squash commits into one?

[seachicken]

Don't worry about it. I do "Squash and merge". I'll release this fix soon as there are some users who need it. Thank you.