chore: replace example for LaTeX to PNG conversion

We might need to use `tikz` package to draw some figures such as graphs,
and this example would be help me discover that feature later.

images/test.tex

@@ -1,7 +1,24 @@
-\documentclass[preview, convert={density=300,outext=.png}]{standalone}
+\documentclass[preview, convert={density=600,outext=.png}]{standalone}
+\usepackage{tikz}
 \begin{document}
-Hello. This is a test.
-\begin{equation}
-L = 2
-\end{equation}
+\begin{tikzpicture}
+      \tikzset{enclosed/.style={draw, circle, inner sep=0pt, minimum size=.15cm, fill=black}}
+
+      \node[enclosed, label={left, yshift=.2cm: E}] (E) at (0.75,3.25) {};
+      \node[enclosed, label={above, xshift=.2cm: H}] (H) at (3,4) {};
+      \node[enclosed, label={right, yshift=0cm: B}] (B) at (4.5,2) {};
+      \node[enclosed, label={below, xshift=.2cm: M}] (M) at (3,0) {};
+      \node[enclosed, label={left, yshift=-.2cm: L}] (L) at (0.75,0.75) {};
+
+      \draw (E) -- (H) node[midway, sloped, above] (edge1) { $\infty$};
+      \draw (H) -- (B) node[midway, right] (edge2) {288};
+      \draw (B) -- (M) node[midway, right] (edge3) {585};
+      \draw (L) -- (M) node[midway, below] (edge4) {$\infty$};
+      \draw (E) -- (L) node[midway, left] (edge5) {640};
+      \draw (E) -- (B) node[midway, above] (edge6) {$\infty$};
+      \draw (E) -- (M) node[midway, left] (edge7) {$\infty$};
+      \draw (L) -- (H) node[midway, left] (edge8) {$\infty$};
+      \draw (L) -- (B) node[midway, below] (edge9) {$\infty$};
+      \draw (H) -- (M) node[midway, right] (edge10) {775};
+\end{tikzpicture}
 \end{document}