Update MSRV to 1.88.0

One or more of the transitive dependencies needs Rust 1.88 or newer, so
this becomes our minimum version. It may be possible to build with an
older Rust by manually picking dependency versions but I'm not going to
do that.

Ideally, `-Zminimal-versions` would pick out those versions, but lots of
crates don't correctly specify minimum depdendency versions. As a
result, our transitive dependencies resolve to
matching-but-non-functional versions.

.gitea/workflows/check.yml

@@ -78,7 +78,7 @@ jobs:
     # https://docs.github.com/en/actions/learn-github-actions/contexts#context-availability
     strategy:
       matrix:
-        msrv: ["1.87.0"]
+        msrv: ["1.88.0"]
     name: ubuntu / ${{ matrix.msrv }}
     steps:
       - uses: actions/checkout@v4

Cargo.toml

@@ -3,6 +3,7 @@ name = "another-boids-in-rust"
 version = "0.7.0"
 edition = "2024"
 license = "AGPL-3.0-only"
+rust-version = "1.88.0"
 
 [dependencies]
 bevy = "0.16.0"