hr: add page (#2426)

pages/common/hr.md

@@ -0,0 +1,15 @@
+# hr
+
+> Print a horizontal rule in the terminal.
+
+- Print a horizontal rule:
+
+`hr`
+
+- Print a horizontal rule with a custom string:
+
+`hr {{string}}`
+
+- Print a multiline horizontal rule:
+
+`hr {{string_a}} {{string_b}} {{string_c}}`