1.81.0 release announcement

[Mark-Simulacrum]

cc @rust-lang/release

[yoshuawuyts]

I saw there is a section in this announcement about the WASI 0.1 target being renamed. In this same release the WASI 0.2 target has also been upgraded from Tier 2 to Tier 3. I just filed a PR for a post explaining what that means in: #1391.

If folks are okay with publishing the WASI 0.2 post on the same day; Maybe we could include a small section at the bottom mentioning that wasm32-wasip2 has reached tier 2 support, and point people interested in that at the longer post? Something like:

### WASI 0.2 target has reached tier 2

The `wasm32-wasip2` target is now supported as a tier 2 target. This means it is
guaranteed to build, can now be installed via `rustup`. To
conditionally target WASI 0.2, the following `cfg` attribute can be used:

```rust
#[cfg(all(target_os = "wasi", target_env = "p2"))]
mod wasip2 {
    // items go here
}
```

For more details see the
[WASI 0.2 tier 2 announcement post](https://blog.rust-lang.org/2024/09/05/wasip2-tier-2.html).