Add figure caption

Author: HenrikBengtsson

OVERVIEW.md

@@ -127,8 +127,12 @@ For a more up-to-date view on what features might be added, see <https://github.
 
 ### Under the hood
 
+
+
 ![](vignettes/figures/slow_sum.svg)
 
+_Figure: Sequence diagram illustrating how signaled progression conditions are captured by `with_progress()` and relayed to the two progression handlers 'progress' (a progress bar in the terminal) and 'beepr' (auditory) that the end user has choosen._
+
 
 ### Debugging
 

vignettes/figures/Makefile

@@ -2,3 +2,6 @@ all: slow_sum.svg
 
 %.svg: %.bob
 	svgbob --font-family=monospace --output $@ < $<
+
+%.png: %.svg
+	inkscape -z -d 192 -e $@ $<