Schema documentation template and naming conventions

[al-v-in]

[al-v-in]

Naming conventions already set by @motey

I've added schema description template to same page, though potentially it should be moved out in to its own page elsewhere when it gets moved across to the new public docs? @Jiros

See https://github.com/covidgraph/documentation/wiki/Adding-your-own-data-to-the-graph

[al-v-in]

@mpreusse please see link above

[Jiros]

Thanks @al-v-in - I'll make a note and bring it across into the new world in some form.