Add single-instance example for CLI init

[ianstanton]

The tembo init command relies on https://raw.githubusercontent.com/tembo-io/tembo/main/tembo-cli/examples/single-instance/tembo.toml, which was removed in this PR:

• moves toml files to examples dir & uses them in tests #487

Now tembo init produces a tembo.toml file with contents 404: Not Found. This PR re-adds the file so it can be used for tembo init.

[ianstanton]

I added the same file that was there before: https://github.com/tembo-io/tembo/blob/72083bff5670fe9aaaf0977598b78ca2ee5ddd43/tembo-cli/examples/single-instance/tembo.toml

[shahadarsh]

I added the same file that was there before: https://github.com/tembo-io/tembo/blob/72083bff5670fe9aaaf0977598b78ca2ee5ddd43/tembo-cli/examples/single-instance/tembo.toml

Just updated a few small things but looks good otherwise.

[shahadarsh]

LGTM 👍