Add Hebrew translations for OHM Time Slider

[yarons]

Added Hebrew as "he" with the appropriate language code, thanks.

[jeffreyameyer]

@yarons - I'm not in the PR approval chain, but I wanted to send a quick "תודה" for taking the time to submit this.

[jeffreyameyer]

@erictheise @1ec5 - not sure which of you is more appropriate for this PR.

[yarons]

Thank you so much @jeffreyameyer!

[1ec5]

Thanks!

[jeffreyameyer]

@1ec5 - soft eta for this going to production is next week, correct? Or, should it be live sooner than that?

[1ec5]

Per OpenHistoricalMap/issues#1057 (comment), this commit hash needs to be updated to point to at least 8d580a3.

We also need to copy-paste this file into https://github.com/OpenHistoricalMap/ohm-website/blob/staging/app/assets/javascripts/leaflet-ohm-timeslider.js, because OpenHistoricalMap/ohm-website#260 created a second copy of the files. Improving how we manage this code has been on the backburner because we intend to replace it entirely: OpenHistoricalMap/issues#914.

[1ec5]

OpenHistoricalMap/ohm-deploy#603