website/docs: add CSP to hardening (#11970) * add CSP to hardening * re-word docs * fix typo * use the correct term "location" instead of "origin" in CSP docs * reword docs * add comments to permissive CSP directives * add warning about overwriting existing CSP headers --------- Signed-off-by: Simonyi Gergő <28359278+gergosimonyi@users.noreply.github.com> Co-authored-by: Simonyi Gergő <28359278+gergosimonyi@users.noreply.github.com> Co-authored-by: Tana M Berry <tanamarieberry@yahoo.com>