fix: add SmoothDamp documentation (#937)

## Changes

Adds documentation for the newly added `TweenService:SmoothDamp` method.

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---------

Author: ramdoys

content/en-us/reference/engine/classes/TweenService.yaml

@@ -123,8 +123,11 @@ methods:
     capabilities: []
     writeCapabilities: []
   - name: TweenService:SmoothDamp
-    summary: ''
-    description: ''
+    summary: |
+      Calculates a value simulating a critically damped spring.
+    description: |
+      Returns a value that allows smoothing a value towards a target simulating a critically damped spring.
+      Supports `Datatype.Vector2`, `Datatype.Vector3`, and `Datatype.CFrame`, and number.
     code_samples: []
     parameters:
       - name: current