Support \hdashline (#1407)

* Support \hdashline

Support `\hdashline` from package `arydshln`. This PR acts as a complement to PR #1395.

Similarly to #1395, the dashed line is rendered as `border-bottom-style: dashed;`. That does not exactly match the `dashsegment` and `dashgap` lengths in `arydshln`, but it does render black lines with sharp edges.

* Fixed top line position

* Add screenshots

* Fix lint error

* Fix another lint error

* Deleted HLine screenshots

* Pick up comments

test/screenshotter/ss_data.yaml

@@ -34,8 +34,8 @@ Alignedat: |
     \end{alignedat}
 Arrays: |
     \left(\begin{array}{|rl:c||}
-        1&2&3\\
-        1+1&2+1&3+1\cr1\over2&\scriptstyle 1/2&\frac12\\[1ex]
+        1&2&3\\ \hline
+        1+1&2+1&3+1\cr1\over2&\scriptstyle 1/2&\frac12\\[1ex] \hline \hdashline
         \begin{pmatrix}x\\y\end{pmatrix}&0&\begin{vmatrix}a&b\\c&d\end{vmatrix}
     \end{array}\right]
 ArrayMode:
@@ -129,7 +129,6 @@ GroupMacros:
         \startExp: e^\bgroup
         \endExp: \egroup
     tex: \startExp a+b\endExp
-Hline: \begin{array}{c|c}\hline \hline \hline  a & b \\ \hline \hline \hline c & d \end{array}  \quad \frac{\begin{pmatrix} a & b \\ \hline c & d \\ \hline \hline \hline\end{pmatrix}} 2  \quad \begin{bmatrix}\hline  a & b \\ \hline c & d \\ \hline e & f \end{bmatrix}
 HorizontalBraces: \overbrace{\displaystyle{\oint_S{\vec E\cdot\hat n\,\mathrm d a}}}^\text{emf} = \underbrace{\frac{q_{\text{enc}}}{\varepsilon_0}}_{\text{charge}}
 KaTeX:
     tex: \KaTeX