release: bump Cargo.toml + lock to 0.10.0 as well

The release ritual only ever touched CMakeLists.txt, so the crate version
had been stale since 0.8.0 — through two releases. That is not cosmetic:
Cargo.toml is the version anyone who runs `cargo install --git` gets, and
`src/main.rs` is a real entry point (it marshals argv into xchplot2_main),
so the installed binary identifies itself as 0.8.0 whatever CMake says.

Both files belong in the bump from here on. A tester reporting a version is
reporting whichever of the two their install path used, and until now those
could differ by two minor releases.

Author: Abraham Sewill

Cargo.lock

@@ -1,6 +1,6 @@
 [package]
 name        = "xchplot2"
-version     = "0.8.0"
+version     = "0.10.0"
 edition     = "2021"
 authors     = ["Abraham Sewill <abraham.sewill@proton.me>"]
 license     = "MIT"