Add missing LoopBack 4 Types docs

[achrinza]

Loosely related: #2527
LoopBack 3-equivilant docs: https://loopback.io/doc/en/lb3/LoopBack-types.html

Steps to reproduce

1. Visit https://loopback.io/doc/en/lb4/Model.html#property-decorator

2. Click the "LoopBack types" link.

   

Current Behavior

The page doesn't exist:

Expected Behavior

The page should exist, describing the different LoopBack types and how they map to the native types of OAS 3, JavaScript and the database engine.

Link to reproduction sandbox

Additional information

N/A

Related Issues

N/A

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[dhmlau]

There is a LB3 version of LoopBack Types: https://loopback.io/doc/en/lb3/LoopBack-types.html. We can possibly use this as the starting point.

[agnes512]

Note: some connector docs for lb4 are using the outdated link. Don't forget to update them as well.