🐞 [Bug]: some examples are not members of workspace

[leighmcculloch]

What happened?

When building some examples inside the repo, an error is shown saying that the example is missing from the workspace members list.

$ cd examples/rwa

$ cargo build --target wasm32v1-none --release
error: current package believes it's in a workspace when it's not:
current:   /home/runner/work/rs-soroban-sdk/rs-soroban-sdk/stellar-contracts/examples/rwa/Cargo.toml
workspace: /home/runner/work/rs-soroban-sdk/rs-soroban-sdk/stellar-contracts/Cargo.toml

this may be fixable by adding `examples/rwa` to the `workspace.members` array of the manifest located at: /home/runner/work/rs-soroban-sdk/rs-soroban-sdk/stellar-contracts/Cargo.toml
Alternatively, to keep it out of the workspace, add the package to the `workspace.exclude` array, or add an empty `[workspace]` table to the package's manifest.

Expected behavior

To be able to build all the examples in the repo.