latin-ext: Missing typographic space characters

Hey!

Merriweather is missing some space characters in the U+2000-U+200A range. For example, U+2002 is absent (but present in the "upstream" font), U+2003 is absent (and absent from "upstream" font), U+202F is absent (and absent from "upstream" font). Last one can be produced with `&nnbsp;` and be used before a double punctuation in French. The rendering depends on the fallback font.