feat: bump title sizes, add font_scale to logo functions, ship SVGs

- Change rel_large default from 16/14 to 20/14 (~1.43x) to match the
  Civilytics editorial design system. Subtitle now renders at 1.0x base
  instead of 0.86x.
- Switch axis.text to rel() sizing so all text elements cascade from the
  root font_size, enabling uniform scaling.
- Add font_scale parameter (default 1.1) to civilytics_logo(),
  add_logo(), and add_logo_ga() — inflates text by ~10% before
  arrangeGrob composition to compensate for viewport shrinkage.
- Ship SVG logo variants (mark, wordmark, pulse) in inst/img/ for
  Quarto/HTML templates.
- Add "Maintaining brand assets" section to README documenting inst/img/
  file inventory and update workflow.
- Document full font size hierarchy in theme_civilytics() roxygen.

man/add_logo_ga.Rd

@@ -2,9 +2,16 @@
 % Please edit documentation in R/logo.R
 \name{add_logo_ga}
 \alias{add_logo_ga}
-\title{Add a logo to a ggplot2 object}
+\title{Add a logo to multiple ggplot2 objects}
 \usage{
-add_logo_ga(plot_list, logo, nrow = 1, widths = NULL, margin_param = NULL)
+add_logo_ga(
+  plot_list,
+  logo,
+  nrow = 1,
+  widths = NULL,
+  margin_param = NULL,
+  font_scale = 1.1
+)
 }
 \arguments{
 \item{plot_list}{a list containing ggplot2 objects}
@@ -16,12 +23,15 @@ add_logo_ga(plot_list, logo, nrow = 1, widths = NULL, margin_param = NULL)
 \item{widths}{an optional vector the same length as plot_list with the widths for each plot}
 
 \item{margin_param}{a number giving the adjustment up or down to help manually align logo and captions}
+
+\item{font_scale}{Numeric. Multiplicative scaling factor applied to text
+sizes before composing. Default `1.1`. See [add_logo()] for details.}
 }
 \value{
 a grid object
 }
 \description{
-Add a logo to a ggplot2 object
+Add a logo to multiple ggplot2 objects
 }
 \note{
 The resulting object needs to be drawn to the screen using grid.draw()