Update pull request template with working links (cdevents#156)

A couple links seems to be outdated which results in 404s. This commit
addresses that by pointing to the CDEvents primer website with the
appropriate sub-links.

Signed-off-by: benjamin-j-powell <benjamin_j_powell@apple.com>
Co-authored-by: benjamin-j-powell <benjamin_j_powell@apple.com>
Co-authored-by: Emil Bäckmark <emil.backmark@ericsson.com>

.github/pull_request_template.md

@@ -8,7 +8,7 @@
 
 As the author of this PR, please check off the items in this checklist:
 
-- [ ] Has the [primer doc](https://github.com/cdevents/spec/blob/main/primer/_index.md) been updated if a design decision is involved
-- [ ] Have the [JSON schemas](https://github.com/tektoncd/community/blob/main/standards.md#tests) been updated if the specification changed
-- [ ] Has spec version and event versions been updated according to the [versioning policy](https://github.com/cdevents/spec/blob/main/primer/_index.md#versioning)
-- [ ] Meets the [CDEvents contributor standards](https://github.com/cdevents/.github/blob/main/docs/CONTRIBUTING.md)
+- [ ] Has the [primer doc](https://github.com/cdevents/cdevents.dev/blob/main/content/en/docs/primer/_index.md) been updated if a design decision is involved
+- [ ] Have the [JSON schemas](https://github.com/cdevents/spec/tree/main/schemas) been updated if the specification changed
+- [ ] Has spec version and event versions been updated according to the [versioning policy](https://cdevents.dev/docs/primer/#versioning)
+- [ ] Meets the [CDEvents contributor standards](https://github.com/cdevents/.github/blob/main/docs/CONTRIBUTING.md)