Adapt examples to be recognised as such by Cargo

[WhyNotHugo]

Currently examples are binary modules inside the workspace. As a result, these are not treated as examples by cargo, e.g.:

> cargo run --example
error: "--example" takes one argument.
No examples available.

This patch moves files around a bit so that examples are actually recognised as such by cargo. This has a few effects:

• cargo test will ensure that they compile.
• They will share the lock file with the main project. This ensure that their dependencies are aligned and avoids potentially downloading and compiling multiple different versions of the same dependency.
• cargo run --example provides useful output:

> cargo run --example
error: "--example" takes one argument.
Available examples:
    editor-libcosmic
    editor-orbclient
    editor-test
    rich-text
    terminal

Depending on the shell's setup, shell completion may also be available when using cargo run --example.

[WhyNotHugo]

CI seems to be failing because some of the dependencies used by examples have licenses that are not explicitly allowed: BSD-3-Clause, Apache-2.0, BSL-1.0, BSD-2-Clause, ISC, MIT, OFL-1.1.

I guess that the previous setup wasn't checking all licences correctly? Note that these are now development dependencies, not dependencies that are built into the crate itself.

[notgull]

-1 to this. Some of these examples have crates with deep dependency trees, and including those in every dev compilation would slow down my own development time.

[WhyNotHugo]

These are only compiled when you run tests. I think that if you’re running tests you’d also want to make sure that examples haven’t broken. Is the build time really even noticeable? Dependencies won’t be recompiled during rebuilds.