Stacking text commands (#1009)

* Adding support for SansSerif-Bold

* Updating to include SansSerif Italic.

* WIP

* Working text stacking

* More robust screenshot.

* Don't want to break users :)

* Updating per PR comments.

* Fixing Unicode and updating snapshots.

* Adding suggested tests.

* Opting to use old method for unit testing.

* Adding TODO

test/screenshotter/ss_data.yaml

@@ -268,6 +268,13 @@ Symbols1: |
     \maltese\degree\pounds\$
     \text{\maltese\degree\pounds\textdollar}
 Text: \frac{a}{b}\text{c~ {ab} \ e}+fg
+TextStacked: 
+  \begin{matrix}
+      \textsf{abc123 \textbf{abc123} \textit{abc123}}\\
+      \text{abc123 \textbf{abc123} \textit{abc123}}\\
+      \textrm{abc123 \textbf{abc123} \textit{abc123}}\\
+      \textsf{\textrm{\textbf{abc123}} \textbf{abc123} \textit{abc123}}\\
+  \end{matrix}
 TextWithMath: \text{for $a < b$ and $ c < d $}.
 Unicode: \begin{matrix}\text{ÀàÇçÉéÏïÖöÛû} \\ \text{БГДЖЗЙЛФЦШЫЮЯ} \\ \text{여보세요} \\ \text{私はバナナです} \end{matrix}
 Units: |