- Move the mixpanel load script to separate file
- Modify the load script to be able to specify which context object
the mixpanel instance should be loaded. Defaults to `window` for
backward compatibility
- Add `context` mixpanel plugin config option that specifies the context
that's passed the refactored load script
- Update hooks to get mixpanel instance from resolveMixpanel function
instead of from `window`. This decouples the use of mixpanel instance
from the window object

- Add option to be able to pass a mixpanel instance directly to
mixpanel plugin instead of fetching it from mixpanel CDN

- Add option to pass Mixpanel config
- The config is passed to mixpanel.init if the instance needs to be
instantiated
- The config is passed to mixpanel.set_config if the instance already
exists

- Add option `pageEvent`, which allows to specify the name of the event
that's tracked when mixpanelPlugin.page is called. Defautlts to 'page'

mixpanelPlugin.page

…able

- If 'mixpanel-browser' npm package is installed, the @analytics/mixpanel
plugin will try to use that if a mixpanel instance doesn't exist yet

current mixpanel instance

- Add ./scripts/types script similar to one in @analytics/core.
  The script postprocesses the generated types and exports plugin config
  and plugin type.
- Add analytics as dependency so types in types.d.ts can import types
- Add 'types' npm command to @analytics/mixpanel
- Add 'temp-types' to .gitignore