Add simple example of library usage and consuming generated output

[Wulf]

Adds a simple example that we use as a compilation test.

We'll need to expand this going forward to ensure robustness

Note: This will fail until #104 is merged in as that fixes a few compilation issues with once_common_* flags

[Wulf]

In the future, we'll want to add actual DB calls using the generate code and either use an in-memory sqlite db or spin up a postgres container to make sure those calls are working

[hasezoey]

Suggested change

	println!("Hello, world!");
	// This file (should) demonstrate the usage of the generated dsync output
	println!("Hello, world!");
	// TODO: This file in the example still needs to be expanded on

add a note so we dont forget the purpose

[hasezoey]

i dont really see why it would require #104, would #112 suffice?

[hasezoey]

i change the title of this PR to better reflect what this PR is doing

[Wulf]

@hasezoey please give this another look when you have the time. It's been a long time since we visited this, so feel free to suggest another approach entirely.

[hasezoey]

Looks mostly good to me now, some small Cargo.toml suggestions and adding some notes.

[hasezoey]

Suggested change

	members = ["todo"]
	members = ["todo"]
	resolver = "2"

remove the cargo warning:

warning: virtual workspace defaulting to `resolver = "1"` despite one or more workspace members being on edition 2021 which implies `resolver = "2"`
note: to keep the current resolver, specify `workspace.resolver = "1"` in the workspace root's manifest
note: to use the edition 2021 resolver, specify `workspace.resolver = "2"` in the workspace root's manifest
note: for more details see https://doc.rust-lang.org/cargo/reference/resolver.html#resolver-versions

[hasezoey]

Suggested change

	println!("Hello, world!");
	// This file (should) demonstrate the usage of the generated dsync output
	println!("Hello, world!");
	// TODO: This file in the example still needs to be expanded on

add a note so we dont forget the purpose

[hasezoey]

Its been a few years since the opening of this PR.
This is still something that would be great to have (dsync as a library usage example), and it is mostly done (aside from maybe adding a simple main impl?)