add solution for day3

src/day_3.jl

@@ -0,0 +1,15 @@
+include(joinpath(readchomp(`git rev-parse --show-toplevel`), "aoc.jl"))
+import .Aoc: @aoc
+
+priority = ['a':'z'; 'A':'Z']
+
+function p1(input::Vector{String})
+    sum([ findfirst(==(intersect(i[begin:sizeof(i)÷2], i[sizeof(i)÷2+1:end])[1]), priority) for i in input ])
+end
+
+function p2(input::Vector{String})
+    sum([ findfirst(==(foldl(intersect, input[i:i+2])[1]), priority) for i in 1:3:length(input) ])
+end
+
+@aoc(2022, 3)
+