add the existing OpenWeatherMap tool to the public api

[zrcni]

OpenWeatherMapAPIWrapper works wonderfully, but the tool itself can't be used in master branch.

• added OpenWeatherMap tool to the public api, to be loadable with load_tools by using "openweathermap-api" tool name (that name is used in the existing docs, at the bottom of the page)
• updated OpenWeatherMap tool's description to make the input format match what the API expects (e.g. London,GB instead of 'London,GB')
• added ecosystem documentation page for OpenWeatherMap
• added tool usage example to OpenWeatherMap's notebook

Let me know if there's something I missed or something needs to be updated! Or feel free to make edits yourself if that makes it easier for you :slightly_smiling_face: