add args flask example and update example env

dotenv

@@ -1,7 +1,20 @@
-DOTENV_MYSQL_ROOT_PASSWORD_OLD=rootpass
-DOTENV_MYSQL_ROOT_PASSWORD=rootpass
+# Example .env file
+DOTENV_MYSQL_ROOT_PASSWORD_OLD=rootp
+DOTENV_MYSQL_ROOT_PASSWORD=rootp
 
 DOTENV_MYSQL_GITEA_PASSWORD=giteap
 DOTENV_MYSQL_FLASK_PASSWORD=flaskp
 
+GITEA_MAIL_FROM=
 
+# Build ARG GPG_PP. May still need to be empty to avoid breakage.
+BUILD_GPG_PP=
+
+
+# Backend:
+
+# Inconsequential token: minimal inconvenience if exposed
+DOTENV_TOKEN_I=dti
+
+# Consequential token: protect
+DOTENV_TOKEN_C=dtc