Switched to non-breaking spaces in Chapter, Volume, Edition, and Page attribution

A very minor change to resolve a bit of acute visual nit-picking. The space in eg, ‘p. 56’, ‘Ch. 7’, ‘Vol. 9’, or ‘(3rd edition)’, created by my attribution logic, could cause the two parts to appear on separate lines in a long attribution string or a narrow viewport. Switching to a non-breaking space ‘ ’ (visually indistinguishable from a normal space) means they will always appear side by side.

Unicode codepoint U+00A0, commonly abbreviated as NBSP.