RELNOTES[NEW]: Add `goog.string.Unicode.ZERO_WIDTH_SPACE`.
RELNOTES[NEW]: Add `goog.string.Unicode.ZERO_WIDTH_SPACE`.

This is useful for word-wrapping in text context (same as <wbr> in HTML context). Zero-width space is an invisible character so it's better to use it in the code indirectly through this enum.

PiperOrigin-RevId: 473309362
Change-Id: Ia8ab342d28d09af1317875da508f7e4b304f09bf

google/closure-library,google/closure-library,google/closure-library,google/closure-library,google/closure-library