Create eo.js

Standard Esperanto keyboard layout (as /usr/share/X11/xkb/symbols/epo for example on Ubuntu) using 10-key-wide variant (ĵ under p) as found eg on official vanilla Android Esperanto layout.  Renders like http://lingvo.org/klavaro/firefoxos.png

The lists of alternate characters are chosen from  CEN WORKSHOP AGREEMENT CWA 13873:2000 (Multilingual European Subsets in ISO/IEC 10646-1) level MES-1 namely àáâãäåæçèéêëìíîïðñòóôõöøßùúûüýþÿāăąćĉċčďđēėęěĝğġģĥħĩīįıĳĵķĸĺļľŀłńņňŉŋōőœŕŗřśŝşšșţťŧțũūŭůűųŵŷźżž, together with characters such as δφγλωπψσθξ from the GSM 03.38 seven bit default alphabet, plus two more letters I noticed already added in the FirefoxOS keyboards ɛ ɵ which I added to avoid regression, and added a few currency symbols.   And noting that no alternate list should be longer than 10 characters.  Ordering is by Unicode number, with the exception of ß so that uppercase S and lowercase s are consistent, and currency symbols are placed last.

Written for https://bugzilla.mozilla.org/show_bug.cgi?id=940041
'&_#%' the same as https://github.com/mozilla-b2g/gaia/pull/16921/files#r17834861.