Update GitHub Pages API to add new response parameters

[rreichel3]

This PR updates the GitHub Pages API structs to support the latest documented response from GitHub.

This fixes#2107

Its based upon the documentation on GitHub's public docs here and enables support for viewing a GitHub Pages' visibility and HTTPS configuration.

[codecov]

Codecov Report

Merging #2109 (62a1c35) into master (b5776f9) will increase coverage by 0.00%.
The diff coverage is n/a.

@@ Coverage Diff @@## master #2109 +/- ##
=======================================
Coverage 97.77% 97.78% =======================================
Files 111 112 +1 Lines 9934 9956 +22 =======================================
+ Hits 9713 9735 +22 
Misses 154 154 Partials 67 67 

Impacted Files	Coverage Δ
github/repos_pages.go	97.11% <ø> (ø)
github/orgs_audit_log.go	100.00% <0.00%> (ø)
github/apps_hooks.go	100.00% <0.00%> (ø)

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[gmlewis]

Thank you, @rreichel3!
Just a few changes, please, and then we should be ready for a second LGTM before merging.

[gmlewis]

Thank you, @rreichel3 !
LGTM.

Awaiting second LGTM before merging.

[rreichel3]

👋 @wesleimp Just wanted to bump this!

[cpanato]

lgtm
thanks for this addition

[gmlewis]

Thank you, @cpanato !
Merging.