Accept TOKEN_FOR_GITEA_WIKI in .env and move the token howto to the wiki

TOKEN_FOR_GITEA_WIKI is an optional key, checked and masked but never used
or asked for, so one .env can serve the wiki publishing too. GITHUB_PAT and
GITHUB_USER are documented as required only when GitHub is chosen.

The how-to for creating the access tokens moves from howto/ to the wiki as
AccessTokens in English, Danish and Bahasa Malaysia, with its pictures in
wiki/img/. README, Home and the sidebar link to it.

Adds MIL-010 with its review RC-033 and the matching plan, user story and
traceability rows.

Task: MIL-010#1
Task: MIL-010#2
Task: MIL-010#3
Closes #83
Closes #84
Closes #85

src/lib/config.sh

@@ -155,6 +155,11 @@ validate_credentials() {
   if [[ -n ${CREDENTIALS[GITHUB_PAT]:-} ]]; then
     SECRET_VALUES+=("${CREDENTIALS[GITHUB_PAT]}")
   fi
+  if [[ -n ${CREDENTIALS[TOKEN_FOR_GITEA_WIKI]:-} ]]; then
+    SECRET_VALUES+=("${CREDENTIALS[TOKEN_FOR_GITEA_WIKI]}")
+    is_valid_token "${CREDENTIALS[TOKEN_FOR_GITEA_WIKI]}" ||
+      die "TOKEN_FOR_GITEA_WIKI in $ENV_FILE is not a valid token ($HINT_TOKEN)"
+  fi
   if [[ -n ${CREDENTIALS[GITEA_TOKEN]:-} ]] &&
     ! is_valid_token "${CREDENTIALS[GITEA_TOKEN]}"; then
     die "GITEA_TOKEN in $ENV_FILE is not a valid token ($HINT_TOKEN)"