Add Strapi CMS with Article and Category content types

Article is deliberately minimal: title, slug, Markdown body, cover image and
category. No Author content type — the administrator is the only writer.

The bootstrap hook grants the Public role find/findOne on the two content types
and disables self-registration, so the public API is read-only and the site has
no front-end accounts.

cms/.env.example

@@ -0,0 +1,8 @@
+HOST=0.0.0.0
+PORT=1337
+APP_KEYS="toBeModified1,toBeModified2"
+API_TOKEN_SALT=tobemodified
+ADMIN_JWT_SECRET=tobemodified
+TRANSFER_TOKEN_SALT=tobemodified
+JWT_SECRET=tobemodified
+ENCRYPTION_KEY=tobemodified