Extend algoliaPost with additional ghost post field

[kassiwin]

The package concerned is algolia-fragmenter specifically the transformToAlgoliaObject function.

Currently, the algoliaPost is hardcoded and the function does not offer any way to add additional fields. It will be interesting to add an optional argument to transformToAlgoliaObject which will help to extend the algoliaPost.

[coelhucas]

Up. It would be awesome to both be able to override or extend these fields (we may not want some or just add a few others).

Right now in order to do that one would have to maintain their own fork just to change a line in fragmenter code 😞

I'm willing to open a PR for this if that's ok for folks at Ghost, just let me know and also if there are any constraints regarding adding that functionality.

[aileen]

Hey hey! PRs are very welcome. Just ensure you don't introduce any breaking changes 😊