Expand client libraries docs with multi-database queries examples

[katarinasupe]

Multi-database queries are not allowed in multicommand transactions.

Query related to multiple databases can be run with neo4j javascript library (e.g.,SHOW DATABASE; USE DATABASE name;)

const { records, summary } = await this._driver.executeQuery(stmt, params, { database: db });

Doesn't work when called with "USE DATABASE memgraph" first.

Workaround:

const session = this._driver.session({database: db});
const result = await session.run(stmt, params);