Update preview2-prototyping download links (#577)

* Update preview2-prototyping download links

This commit updates the preview2-prototyping command and reactor .wasm
download links as they have been updated.

Signed-off-by: Daniel Bevenius <daniel.bevenius@gmail.com>

* Change component adapter links to point to wasmtime

This commit updates the link to the component adapters to point to the
wasmtime repository instead of preview2-prototyping.

Signed-off-by: Daniel Bevenius <daniel.bevenius@gmail.com>

---------

Signed-off-by: Daniel Bevenius <daniel.bevenius@gmail.com>

README.md

@@ -154,8 +154,10 @@ which has a `_start` entrypoint (e.g. a `src/main.rs` in Rust).
 
 [preview2-prototyping]: https://github.com/bytecodealliance/preview2-prototyping
 [preview1-build]: https://github.com/bytecodealliance/preview2-prototyping/releases/tag/latest
-[non-command]: https://github.com/bytecodealliance/preview2-prototyping/releases/download/latest/wasi_snapshot_preview1.reactor.wasm
-[command]: https://github.com/bytecodealliance/preview2-prototyping/releases/download/latest/wasi_snapshot_preview1.command.wasm
+[non-command]: https://github.com/bytecodealliance/wasmtime/releases/latest/download/wasi_snapshot_preview1.reactor.wasm
+[command]: https://github.com/bytecodealliance/wasmtime/releases/latest/download/wasi_snapshot_preview1.command.wasm
+
+
 
 ## Supported Guest Languages
 [guests]: #supported-guest-languages