Convert lambda function to typescript

[NickRoach]

Part of #67 It's vanilla javascript at the moment, so it can be hard to spot potential runtime errors while making changes. Convert it to typescript. Don't convert dispatchLambda, let's just leave that as vanilla js.

• [ ] Rename blackheathWeatherLambda.js to .ts
• [ ] Set up typescript transpilation to generate a javascript output file. This will likely require a package.json in the lambda directory.
• [ ] Define any types that cannot be determined implicitly i.e. const bucket_name = "thenameofthebucket" doesn't need a type definition because the typescript compiler knows that's a string
• [ ] Modify the deployment script to do transpilation to javascript before the pulumi deployment

[NickRoach]

@burtscriptor I have now set up a dev environment so we can start working on the #67 epic. You're welcome to have a go at this, but I suggest you try #101 first