Pull request templates link to a non-existent issue form #225

.github/PULL_REQUEST_TEMPLATE/bug_fix.md and improvement.md (line 32) link to ../ISSUE_TEMPLATE/new?template=….md. In a rendered pull request description this is a relative path that leads to no issue form.

Fix: link to https://github.com/eclipse-score/<repo>/issues/new/choose, or to …/issues/new?template=bug_fix.md / improvement.md once the issue templates are recognised (see the front-matter issue).

Found by the Copilot review of eclipse-score/contributor_training#2, which carries both files unchanged.