docs: add version requirements to v7 migration docs

Author: SethFalco

docs/migrating_to_7.md

@@ -11,6 +11,7 @@ you should be aware of when migrating from Mongoose 6.x to Mongoose 7.x.
 
 If you're still on Mongoose 5.x, please read the [Mongoose 5.x to 6.x migration guide](migrating_to_6.html) and upgrade to Mongoose 6.x first.
 
+* [Version Requirements](#version-requirements)
 * [`strictQuery`](#strictquery)
 * [Removed `remove()`](#removed-remove)
 * [Dropped callback support](#dropped-callback-support)
@@ -28,6 +29,12 @@ If you're still on Mongoose 5.x, please read the [Mongoose 5.x to 6.x migration
   * [Removed `LeanDocument` and support for `extends Document`](#removed-leandocument-and-support-for-extends-document)
   * [New parameters for `HydratedDocument`](#new-parameters-for-hydrateddocument)
 
+## Version Requirements {#version-requirements}
+
+Mongoose now requires Node.js >= 14.0.0 and MongoDB >= 5.0.0.
+
+See [the MongoDB Node drivers migration guide](https://github.com/mongodb/node-mongodb-native/blob/main/etc/notes/CHANGES_5.0.0.md) for detailed info.
+
 ## `strictQuery` {#strictquery}
 
 `strictQuery` is now false by default.