Added a oneliner referring to the website and removed pr01.adoc

[larsbarring]

See issue #383 for discussion of these changes.

Release checklist

• [NA] Authors updated in cf-conventions.adoc?
• [NA] Next version in cf-conventions.adoc up to date? Versioning inspired by SemVer.
• history.adoc up to date?
• [NA] Conformance document up-to-date?

For maintainers

To make use of the new theme file a small change has to be made to the github workflow file adoc_build.yml:

...
shellcommand: 'asciidoctor-pdf --verbose ${FINAL_TAG} -d book --theme default-theme-CF-version.yml \
cf-conventions.adoc -D conventions_build'
...

(the [relative] path the the theme file might have to be changed)

After the merge remember to delete the source branch.
Tags are set at the conclusion of the annual meeting; until then master always is a draft for the next version.