Improve docs for installing dioxus-cli: needs --locked parameter

I don't know if this is the right place to report :

Command line to install dx doesn't work: `cargo install dioxus-cli@0.7.0-alpha.1` and even with -rc.0 version.

I had this issue
https://github.com/DioxusLabs/dioxus/issues/4705

And solution provided in https://github.com/DioxusLabs/dioxus/issues/4661 resolves the problem.

Solution: Add `--locked` parameter to cargo install command.

```
cargo install dioxus-cli:0.7.0-rc.0 --locked
```

It was not trivial to find this solution. Probably would be nice to add to bevy 0.17 announcement.

_Originally posted by @PPakalns in https://github.com/bevyengine/bevy-website/issues/2254#issuecomment-3343846188_

Start with the Bevy 0.17 announcement and its dioxus-cli installation instructions; compare the documented cargo install command with the working command described here. Done means the installation guidance includes --locked and reflects the versioned command that resolves the reported problem.

Written by the indexing model from the issue text.