Add J solution for day 5.

day5.ijs

@@ -0,0 +1,4 @@
+bs2n =: 3 : '+/ "1(|.*/\(1,(_1+#y)$2)) *"(1) 0 "."0 y'
+ns =: bs2n "1 'F0B1L0R1' charsub > cutopen 1!:1 < jpath '~/projects/AoC/2020/year2020day5.txt.cache'
+>./ns
+(<./ns)+I.-.((<./ns)+i.#ns)e.ns