Put on crates.io, make the API stable enough to use as a standalone library

[nukep]

I don't feel that LlamaDB is at a point where it can serve as a standalone library yet. The library crate is currently a bunch of hacks that expose internals such as parser modules.

This issue needs to wait on #4 so that developers have a somewhat reasonable API to work with, as well as a file-based DB. tempdb won't be around for long!

Until then, the llamadb crate has been reserved on crates.io.

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Nice-to-haves for the library:

• A sql!() macro that statically validates and compiles the SQL query (to an extent).
  • This may be hard to do without schema information.
  • At least have it validate the syntax, possibly compile into AST?
• A C API, for use by other programming languages.