Now that #385 is merged, add CLI versions of those methods.

```sh

init spatialite

sqlite-utils init-spatialite database.db

or maybe/also

sqlite-utils create database.db --enable-wal --spatialite

add geometry columns

needs a database, table, geometry column name, type, with optional SRID and not-null

this needs to create a table if it doesn't already exist

sqlite-utils add-geometry-column database.db table-name geometry --srid 4326 --not-null

spatial index an existing table/column

sqlite-utils create-spatial-index database.db table-name geometry ```

Should be mostly straightforward. The one thing worth highlighting in docs is that geometry columns can only be added to existing tables. Trying to add a geometry column to a table that doesn't exist yet might mean you have a schema like {"rowid": int, "geometry": bytes}. Might be worth nudging people to explicitly create a table first, then add geometry columns.