Preserve multiple mid-line space in autogen /$ (#1718)

In GG1, `/$` markup not only indents using an HTML span
with margin, but also replaces pairs of mid-line spaces with
`  `. Without that, HTML compresses the multiple
spaces to one, which is not what is wanted.

This makes GG2 do the same. Fixes #1717

Author: windymilla

src/guiguts/html_convert.py

@@ -667,6 +667,10 @@ def maybe_close_chapter_div(chapter_div_open: bool, next_step: int) -> int:
         # lines within "/$" or "/*" markup
         if dollar_nowrap_flag or asterisk_nowrap_flag:
             do_per_line_markup(selection, line_start, line_end, ibs_dict)
+            # Preserve mid-line multiple spaces for "/$"
+            if dollar_nowrap_flag:
+                nbsp_sel = re.sub("  ", "  ", selection.lstrip())
+                maintext().replace(line_start, line_end, nbsp_sel)
             # Add 0.5em margin per space character
             if n_spaces > 0:
                 maintext().insert(