chore: remove 'verify' function

[billiegoose]

BREAKING CHANGE: The verify function has been removed, and the signature property of TagObject renamed to gpgsig to match CommitObject. Since log, readCommit, and readTag all include the gpgsig and signing payload in their return values now, it is simpler and more efficient to do the verification outside of isomorphic-git. See the documentation for the onSign parameter for complete code examples.

[isomorphic-git-bot]

Thank you wmhilton! I auto-formatted the code using prettier-standard. 🤖

[karma-pr-reporter]

Test Results for 0069588:

Browser	Pass	Skip	Fail	Time	Disconnect?
Chrome 79.0.3945 (Windows 10 0.0.0)	360	1	0	2m:7s	false
Chrome Mobile 78.0.3904 (Android 0.0.0)	360	1	0	1m:41s	false
Firefox 72.0.0 (Ubuntu 0.0.0)	360	1	0	0m:36s	false
HeadlessChrome 0.0.0 (Linux 0.0.0)	360	1	0	0m:29s	false
Mobile Safari 13.0.0 (iOS 13.0.0)	360	1	0	2m:30s	false
Safari 13.0.3 (Mac OS X 10.15.1)	360	1	0	3m:19s	false

Longest running tests

• 11.475 secs - walk can populate type, mode, oid, and content - Safari
• 8.316 secs - fetch fetch --prune-tags from git-http-mock-server - Safari
• 6.16 secs - checkout checkout file permissions - Safari
• 6.127 secs - statusMatrix statusMatrix with filter - Safari
• 5.135 secs - fetch fetch --prune from git-http-mock-server - Mobile Safari
• 4.875 secs - Hosting Providers GitLab fetch - Safari
• 4.855 secs - Hosting Providers AWS CodeCommit push - Mobile Safari
• 4.845 secs - merge merge 'add-files' and 'remove-files' - Safari
• 4.79 secs - status status - Safari
• 4.742 secs - walk can populate type, mode, oid, and content - Chrome
• 4.677 secs - fetch shallow fetch (from Github) - Chrome Mobile

[isomorphic-git-bot]

🎉 This PR is included in version 1.0.0-beta.24 🎉

The release is available on:

• npm package (@beta dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[isomorphic-git-bot]

🎉 This PR is included in version 1.0.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀