ui-blame: Allow syntax highlighting

Place file contents into a single block so that syntax highlighting can
be applied in the usual fashion.  Place the alternating color bars
behind the file contents.  Force the default syntax highlighting
background to transparent.

Signed-off-by: Jeff Smith <whydoubt@gmail.com>
Reviewed-by: John Keeping <john@keeping.me.uk>

filters/syntax-highlighting.py

@@ -34,7 +34,7 @@ sys.stdin = io.TextIOWrapper(sys.stdin.buffer, encoding='utf-8', errors='replace
 sys.stdout = io.TextIOWrapper(sys.stdout.buffer, encoding='utf-8', errors='replace')
 data = sys.stdin.read()
 filename = sys.argv[1]
-formatter = HtmlFormatter(style='pastie')
+formatter = HtmlFormatter(style='pastie', nobackground=True)
 
 try:
 	lexer = guess_lexer_for_filename(filename, data)