Heading 5 and 6 (title 5 and 6) are too small wrt regular text in flamingo

In Flamingo, with default color theme, the heading level 5 is the same size as the regular text while the heading 6 is smaller than regular text.

In addition, in the default color theme for 6.4-SNAPSHOT, the titles colors are black (same as text color), so heading 5 is impossible to differentiate from the regular text. See the attached image, for the following wiki syntax:

Test regular text

==== title 4====

Test regular text

===== title 5 =====

test regular text

====== title 6 ======

test regular text