Add block, example, alert blocks to latex snippets

snippets/tex.snippets

@@ -229,4 +229,15 @@ snippet sum
 	\sum^{${1:n}}_{${2:i=1}} ${3}
 snippet lim
 	\lim_{${1:x \to +\infty}} ${2}
-
+snippet block
+	\begin{block}{${1:title}}
+	${2}
+	\end{block}
+snippet alert
+	\begin{alertblock}{${1:title}}
+	${2}
+	\end{alertblock}
+snippet example
+	\begin{exampleblock}{${1:title}}
+	${2}
+	\end{exampleblock}