Relative font sizes

[eroten]

In council_theme(), we have each font size as its own parameter. I'd like to modify the function so that you can use specific sizes OR use a base font size and generate font sizes using a relative multiplier

For example

# current setup
size_header <- 22
size_axis_title <- 14

# new setup

base_size <- 12
size_header <- round(base_size *  1.8, digits = 0)
size_axis_title <- round(base_size * 1.1,  digits = 0)

We will need to establish what multiplier to use for each element and have some sort of limit on the font size (nothing smaller than 8). There is likely some general rule for text hierarchy in graphic design to be found out there.

[eroten]

Duplicate of #23