fix: TS 4.5 fixes

Author: avaly

src/mongo_types.ts

@@ -56,7 +56,7 @@ export type WithoutId<TSchema> = Omit<TSchema, '_id'>;
 
 /** A MongoDB filter can be some portion of the schema or a set of operators @public */
 export type Filter<TSchema> = {
-  [P in Join<NestedPaths<TSchema>, '.'>]?: Condition<PropertyType<TSchema, P>>;
+  [Property in Join<NestedPaths<TSchema>, '.'>]?: Condition<PropertyType<TSchema, Property>>;
 } & RootFilterOperators<TSchema>;
 
 /** @public */
@@ -434,7 +434,7 @@ export type Join<T extends unknown[], D extends string> = T extends []
   ? `${T[0]}`
   : T extends [string | number, ...infer R]
   ? `${T[0]}${D}${Join<R, D>}`
-  : string | number;
+  : string;
 
 /** @public */
 export type PropertyType<Type, Property extends string> = string extends Property