Upload initial set of templates

[ronaldtse]

We currently have 3 sets of templates:

• https://github.com/metanorma/annotated-express
• https://github.com/metanorma/iso-10303-detached-docs
• https://github.com/metanorma/iso-10303-srl (04-schemas.adoc as generated by stepmod2mn)

We need to use a single shared set, which will be stored in this very repository.