I've tried to import the script into my project and i notice that my character begins to jitter when it enters in collision with the ground. I've notice that in your project you enabled the project settings physics 2D option "AutoSyncTransforms". Due to performance issues this is not recommended by Unity (https://docs.unity3d.com/ScriptReference/Physics2D-autoSyncTransforms.html). The cleanest way to fix this problem is moving your character demo logic from "Update" to "FixedUpdate". This because Unity will always sync transforms in a moment after the update function and before the first FixedUpdate of the frame.
I've tried to import the script into my project and i notice that my character begins to jitter when it enters in collision with the ground. I've notice that in your project you enabled the project settings physics 2D option "AutoSyncTransforms". Due to performance issues this is not recommended by Unity (https://docs.unity3d.com/ScriptReference/Physics2D-autoSyncTransforms.html). The cleanest way to fix this problem is moving your character demo logic from "Update" to "FixedUpdate". This because Unity will always sync transforms in a moment after the update function and before the first FixedUpdate of the frame.