minor changes (spelling, md, grammar)

.github/SECURITY.md

 Please report security vulnerabilities to mislav@github.com. Thank you!
 
-Note that, unlike [GitHub CLI](https://github.com/cli/cli), hub is _not_ an elegible target for the [GitHub Bug Bounty program](https://hackerone.com/github).
+Note that, unlike the [GitHub CLI](https://github.com/cli/cli), `hub` is _not_ an eligible target for the [GitHub Bug Bounty program](https://hackerone.com/github).