Docs fix: `10updocker cert` tools should instruct user to restart site

[benlk]

Troubleshooting

• [X] I have attempted to troubleshoot this already

Describe the bug

10updocker cert generate example.test followed by 10updocker cert install doesn't install the cert in the running site, until the site's docker is restarted.

Steps to Reproduce

1. Find a site on your local with an expired cert. Suggestions: a project you've been working on for more than a year, or that you haven't worked on in a while
2. Verify that the cert is expired.
3. 10updocker cert generate example.test for this site
4. 10updocker cert install
5. Reload the site: the cert is not used
6. 10updocker restart
7. Reload the site: the cert is used

Screenshots, screen recording, code snippet

No response

Environment information

• Device: MacBook Intel
• OS: macOS Catalina, 10.15
• Browser: Chrome
• 10updocker version: 3.0.2
• 10updocker documentation version: as installed, plus the current version of this repo's README

Code of Conduct

• [X] I agree to follow this project's Code of Conduct

[benlk]

Suggested fixes:

• add a note to the cert generation default output reminding the user to install the cert
• add a note to the cert install output reminding the user to restart the site or Docker
• add a note to the README to remind the user to restart the site or Docker