Add description for @ctx ParameterDecorator in apollo-server/edit/main/docs/source/data/context.mdx
### Issue Description

Spent 15 minutes to understand, how to catch context defined in _ApolloServer_ class instance 
in my resolver, what was created in according youtube video where _@Resolver(of=>)_ and _@Query((returns) => )_ applied

M.b. some little reference ))

Thanx for that

### Link to Reproduction

https://www.apollographql.com/docs/apollo-server/data/context/

### Reproduction Steps

_No response_