harcoded font sizes.

[iampritishpatil]

Currently, the font sizes, especially for the abstract, appear to be hardcoded at 9pt, which is a bit small. We might consider adding a field to

#pubmatter.show-title-block 
and 
#pubmatter.show-abstract-block 

Alternatively, we could remove the hardcoded font sizes altogether. This would allow the outer style to be chosen by default and customized as needed, perhaps using a format like:

#text(size: 12pt)[#pubmatter.show-abstract-block(fm)]