Refactor 2D Renderer and add ASCII observation type (#53)

* Refactor 2D rendering code in `GridEnv` to improve performance and readability.
* Dynamic resolution support for 2D and 3D rendering in `GridEnv` using the `resolution` argument.
* Adds `ascii` observation type for `GridEnv`.

Fix for 3D textures on reinitialization (#52)

* Fixes 3D textures when environment class is reinitialized within a single python session.

Improve rendering efficency (#51)

* Refactors 2D and 3D renderers for `GridEnv`.
* 3D renderer is now roughly 10x faster than before.

Manual reward collection (with test) (#49)

* Adds manual reward creation
* Adds test for this feature
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Co-authored-by: quendera <[email protected]>

Show reward value in symbolic obs (#46)

Minor version bump

GraphEnv `torch_obs` (#45)

* Add `torch_obs` flag to `GraphEnv`.
* Fix bug in 3d observation dimension order in `GridEnv`.

Fix dependency

Fix bug in 2D grid rendering (#43)

Bump version number (#42)

* Bump version number