fix: update links in the templates

[zxc-w]

Checklist:

• [x] I have read freeCodeCamp's contribution guidelines.
• [x] My pull request has a descriptive title (not a vague title like Update index.md)

Closes #620

I have checked all the templates and the first two changes are: https://contribute.freecodecamp.org/how-to-open-a-pull-request/#prepare-a-good-pr-title instead of https://contribute.freecodecamp.org/#/how-to-open-a-pull-request?id=prepare-a-good-pr-title

and https://contribute.freecodecamp.org/intro/ instead of https://contribute.freecodecamp.org/#/

Although both is working, i think that the first link is the preferred one in each of them.

The third change was to embed the link into the text. And the fourth was the one mentioned in the issue.