…295)

Closes #291 

This updates the serde types to incorporate the changes to the LDtk
quicktype file between versions 1.4.1 and 1.5.3. It also updates the
examples to use LDtk 1.5.3.

Closes #259
Also, I think updating to 0.12 implicitly...
Closes #233
Closes #111

This PR upgrades the `bevy` dependency to `0.12`, as well as
`bevy_ecs_tilemap` to `0.12`. For dev-dependencies, it also upgrades
`bevy_rapier2d` to `0.23`, and `bevy-ecs-egui` to `0.21`. Most other
changes were just necessary to get the lib/tests/doc-tests/examples to
compile.

This was a little more complicated for `ldtk_external_level.rs` and
`ldtk_project.rs` since they are updating to use bevy assets v2.
However, using assets v2 did help improve these modules slightly. In
particular, it was easier to add dependent assets to the load context,
and having an associated type for the error allowed me to remove the
dependency on `anyhow` entirely.

Another slightly more difficult update was the `process_ldtk_assets`
system. However, I'm quite happy with the distinction betwen
`AssetEvent::Added` and `AssetEvent::LoadedWithDependencies`.
`bevy_ecs_ldtk` now waits for the latter before spawning levels, which
is functionally what it meant to do originally.

I've verified that all the examples are visually OK, and also checked
out some visual edge cases. Any visual bugs I noticed aren't new.

Will keep this as a draft until `bevy_ecs_tilemap` 0.12 releases.

…ely loaded (#296)

Sorry @MScottMcBee I accidentally merged your branch into the already
merged feat/bevy-0.12. For actual PR this is attempting to merge is
#281.

---------

Co-authored-by: Michael "Scott" McBee <mscottmcbee@gmail.com>

Forgot to run CI on this PR before merging it. This should make the CI
happy going forward.

…ctions (#282)

Now that the "introductory chapters" of the book are complete, the book
can now be referenced by other repository documentation. In particular -
the getting started guide and explanation of "game logic integration"
were both already existing in a lesser form in the API ref and
README.md. These sections have been replaced by references to the books
documentation, and the *tile-based game tutorial*/*game logic
integration* chapters respectively.

This new chapter explains and compares the strategies for spawning
levels:
- `LevelSelection`
- `LevelSet`
- `load_level_neighbors`...

In writing this, I realized this was actually a better first explanation
chapter for the book than *Game Logic Integration*, so I've placed it
first and also referenced it directly in `README.md`, `src/lib.rs`, and
the book introduction.

Any explanations in the API reference made redundant by this chapter
have been updated to reference the chapter instead.

This new chapter explains in greater detail the results of spawning the
world/levels. This includes the explanation of the hierarchy, worldly
entities, tile metadata, level backgrounds, layers with colliding tiles,
and z ordering.

Redundant explanations in the API reference have been replaced by
references to this chapter.