typescript/prefer-namespace-keyword Style
What it does
This rule reports when the module keyword is used instead of namespace. This rule does not report on the use of TypeScript module declarations to describe external APIs (declare module 'foo' {}).
Why is this bad?
Namespaces are an outdated way to organize TypeScript code. ES2015 module syntax is now preferred (import/export). For projects still using custom modules / namespaces, it's preferred to refer to them as namespaces.
Example
typescript
module Example {}