Remove "_blank" Link Targets

[ntno]

115 - do not force new window/tab on link click

Description

• removes use of target="_blank" in documentation site
• remove use of target="_blank" in theme footer and revision block

References

• https://yale.app.box.com/s/ochc2c7zzhsj4wuk6fv41hbk5w8vhxt5
• https://css-tricks.com/use-target_blank/
• https://adrianroselli.com/2020/02/link-targets-and-3-2-5.html

Testing

• [x] This change adds test coverage for new/changed/fixed functionality

Checklist

• [ ] I have added documentation for new/changed functionality in this PR or in mkdocs-terminal/documentation
• [x] All active GitHub checks for tests, formatting, and security are passing