feat: Added AnchorToEffect and AnchorByEffect

[st-pasha]

Description

• Added AnchorProvider interface, currently implemented by PositionComponent and Viewfinder.
• Added AnchorToEffect and AnchorByEffect that can be applied to a target which is an AnchorProvider.

Checklist

• The title of my PR starts with a Conventional Commit prefix (fix:, feat:, docs: etc).
• I have read the Contributor Guide and followed the process outlined for submitting PRs.
• I have updated/added tests for ALL new/updated/fixed functionality.
• I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• I have updated/added relevant examples in examples.

Breaking Change

• [-] Yes, this is a breaking change.
• No, this is not a breaking change.

[wolfenrain]

LGTM

[st-pasha]

It just occurred to me that AnchorByEffect will also be useful to have.

[erickzanardo]

Can you share a use case for this? Just really curious, never thought myself on animating a component anchor

[st-pasha]

We already have Anchor effects in the current camera, only it's called relativeOffset there, and when you call setRelativeOffset(Anchor newRelativeOffset), it applies a smooth transition of the anchor. So, AnchorToEffect() is an equivalent mechanism for the new camera, but allows a finer control over the timing of the transition.

Then, there is camera shake. It can also be done via an effect -- either affecting the camera's position, or the camera's anchor. It occurs to me that doing the shake via an anchor effect would be more reliable, since the camera's position is already affected by various behaviors such as follow-component of world-boundary. So, this is where AnchorEffect.by would come in: add a tiny amount of random offset to the camera's anchor, and it shakes nicely without any interference from the position behaviors.