added matrix + vector functions

gallery/example2.typ

@@ -0,0 +1,30 @@
+#import "/src/lib.typ": *
+
+#let v1 = vec.vec(1, 2, 3)
+#let v2 = vec.vec(4, 5, 6)
+
+#let v3 = vec.add(v1, v2)
+#let v4 = vec.sub(v1, v2)
+#let d = vec.dot(v1, v2)
+#let v5 = vec.cross(v1, v2)
+
+$arrow(v_1) = #vec.display(v1) quad arrow(v_2) = #vec.display(v2)\
+ arrow(v_1) + arrow(v_2) = #vec.display(v3)\
+ arrow(v_1) - arrow(v_2) = #vec.display(v4)\
+ arrow(v_1) dot arrow(v_2) = #d\
+ arrow(v_1) times arrow(v_2) = #vec.display(v5)\
+$
+
+#let m = mat.mat(
+  (1, 2),
+  (3, 4)
+)
+#let v = vec.vec(
+  5,
+  6
+)
+
+#let mv = mat.mul-vec(m, v)
+
+$M = #mat.display(m) quad V = #vec.display(v)\
+M V = #vec.display(mv)$