Rename method to in Monitor class and add tests

[KqLLL]

When I use the cronitor-js SDK to get monitor data, the data method always throws an error saying "data is not a function." So I checked the code and found that the monitor has a property also called data, which overrides the method.

    const cronitorClient = getCronitorClient();
    const monitorInstance = new cronitorClient.Monitor(alert.id);
    console.log('monitorInstance.data:', monitorInstance.data);

    const response = await monitorInstance.data() as IMonitor;

[KqLLL]

@aflanagan Hello, can you take a look at this PR?

[aflanagan]

wow, good catch, thank you!