Add related links for writing a standard/principle on the respective standards/principles listing pages

[keithkennedyHO]

Which content do you think should be reviewed?

• On the standards page add, as a related link, Writing a standard.
• On the principles page add, as a related link, Writing a principle.

Content should be reviewed once ACP migration is complete.

Additional information The writing a standard link was removed in #271

Please confirm the below

• [x] I have checked through the issues on the repository and don't think this has already been suggested