meta_project: specify and document Rust 1.74 MSRV

This isn't required for the libraries published to crates.io,
so this isn't specified in the workspace Cargo.toml.

examples/meta_project/rust/main/Cargo.toml

@@ -8,6 +8,10 @@ version = "0.1.0"
 authors = ["Andrew Hayzen <[email protected]>"]
 edition = "2021"
 license = "MIT OR Apache-2.0"
+# Linking CXX-Qt crates as rlibs requires a compiler feature
+# that was stabilized in Rust 1.74,
+# combining +whole-archive and +bundle link modifiers: https://github.com/rust-lang/rust/pull/113301
+rust-version = "1.74"
 
 [lib]
 crate-type = ["staticlib"]