Use a real cargo workspace

[mondeja]

Currently the library is located at the root and the examples reside in a workspace/ subdirectory that is not a cargo workspace.

The tree should be updated to:

• leptos-hotkeys/ folder (or with the _ character as separator, I don't care)
• examples/ folder

And define the examples directory in the root Cargo.toml at workspace.members. This would allow to check examples when running cargo clippy and cargo check, share the same target folder, it would allow users to easily know where examples are...