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/figures/fig-bulk-fermentation.tex

@@ -8,7 +8,7 @@
   \node [block, below of=dough_ready] (divide_preshape) {\footnotesize Divide and preshape};
   \node [decision, below of=smell] (dough_flattened) {\footnotesize Dough flattened out?};
   \node [block, left of=dough_flattened] (stretch_fold) {\footnotesize Stretch and fold};
-  \node [block, left of=smell] (wait_60_minutes) {\footnotesize Wait 60 minutes};
+  \node [block, left of=smell] (wait_60_minutes) {\footnotesize Wait 60~minutes};
 
   \path [line] (init) -- (check_dough);
   \path [line] (check_dough) -- (size_increase);