[DOCS] Create internal guidelines on how to write documentation

[xelaint]

📄 Documentation Request

What were you doing?

Documentation language is all over the place in Daffodil.

Expected behavior

Set of internal guidelines on how to write documentation. Language, syntax, formatting, etc.

Existing Documentation

None

Environment

Daffodil version: X.Y.Z
Angular version: X.Y.Z 

 
For Tooling issues:
- Node version: XX  
- Platform:  

Others: