Use Siunitx package for dealing with units (#129)

It is complicated :
[1] The International System of Units (si), https://www.bipm.org/en/
measurement-units/.
[2] International System of Units from nist, http://physics.nist.gov/cuu/Units/
index.html.

And one will never get it right (space or not, half-space?) nor
consistent so using that instead.

I am not sure how times and hours, when to write digits and when in
letter so I did not change much..

Did not touch the tables as ebooks on github actions seems to break when
you look at them funny.

Co-authored-by: Cedric <ced@awase.ostal>

book/book.tex

@@ -15,6 +15,7 @@
 \usepackage{chemformula}
 \usepackage{booktabs}
 \usepackage{makecell}
+\usepackage{siunitx}
 
 \renewcommand\theadfont{\bfseries}
 
@@ -74,6 +75,7 @@
 \usepackage{caption}
 \captionsetup[figure]{font=footnotesize}
 
+\DeclareSIUnit\degF{\text{°}F}
 % Basic attributes
 \author{Hendrik Kleinwächter}
 \title{The Sourdough Framework}