Add new unit/qualifier (thermal) and showcase

bib/glossaries/symbols/subscripts.bib

@@ -17,4 +17,8 @@ @symbol{air
 @symbol{electric,
  name={\text{el.}},
  description={electric},
-}
+}
+@symbol{thermal,
+ name={\text{th}},
+ description={thermal},
+}

chapters/mainmatter/base-features.tex

@@ -480,6 +480,9 @@ \subsubsection{Physical Units}
 The mode in which units with negative exponents are displayed can be changed,
 \iecfeg{e.g.}\ fractions can be used:
 \si[per-mode=fraction]{\meter\cubed\kelvin\per\kilogram\squared\per\giga\watt\per\degreeCelsius}.
+You can also use \verb|\DeclareSIQualifier| to create textual subscripts for units,
+further specifying them, or create entirely custom units using \verb|\DeclareSIUnit|.
+An example for both combined is: \si[per-mode=fraction]{\mega\watthour\thermal\per\meter\cubed}.
 
 The \verb|\SI{<quantity>}{<unit>}| command essentially combines \verb|\num| and
 \verb|\si|, inserting a small space in between, for correct typesetting.

cookbook.cls

@@ -1655,7 +1655,7 @@
  % Declare units ourselves:
  % Set as text so it stays a hyphen in math mode, as opposed to minus sign
  \DeclareSIUnit{\volpercent}{Vol.\text{-}\%}
- \DeclareSIUnit{\kilowatthour}{kWh}%
+ \DeclareSIUnit{\watthour}{Wh}%
  \DeclareSIUnit{\annum}{a}%
  \DeclareSIUnit{\atmosphere}{atm}%
  \DeclareSIUnit{\partspermillion}{ppm}%
@@ -1669,6 +1669,9 @@
  \DeclareSIQualifier{\water}{%
  \glsfmtname{sub.water}%
  }
+ \DeclareSIQualifier{\thermal}{%
+ \glsfmtname{sub.thermal}%
+ }
 
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