feat: Stream contents of location file instead of reading it at once

[m-h-t]

Hi @kyleai

This PR implements stream reading chunks of the location file consecutively instead of loading it all into memory. I did this because Chromium froze when trying to calculate my travelled distance as the JSON file was too big.

I also added webpack, changed the structure somewhat; it now displays km instead of miles... If you decide to merge, feel free to cherry pick the changes you want. Also, it'd be great to have an option to choose between miles/km and date formats. :-)

Fixes https://github.com/kyleai/Google-Location-History-Total-Distance-Travelled/issues/1