Set default font to Calibri

That's what's used as the main font in the ESCAPE Word template (although they
also scatter in some Arial to stop things from being too easy).

main.tex

@@ -6,6 +6,8 @@
 \documentclass[note]{astron}
 \usepackage{csquotes}
 \usepackage{subcaption}
+\usepackage{fontspec}
+\IfFontExistsTF{Calibri}{\setmainfont{Calibri}}{}
 
 \input{meta}
 \input{changes}