Document recommendation for instantiating/managing validator instances

[rodaine]

Title. A few strategies are available, but want to encourage folks to reuse a validator instead of creating a new one for every call to Validate.

[Masedko]

You can compare this to the database instance. You create a database instance that you use everywhere, instead of creating a new one every time you need to query something. The same goes with validator instance

[rodaine]

I like that, @Masedko!