Add day 6 solution.

2020/lib/util/strings.go

@@ -0,0 +1,21 @@
+package util
+
+// Takes a slice of strings as from reading each line in a file.
+// Concatenates strings, creating new ones when blank lines are encountered
+// NB: adds a single space to the beginning of each concatenated line.
+func SplitOnBlankLine(input []string) []string {
+	converted := []string{}
+
+	current := ""
+	for _, line := range input {
+		if line == "" {
+			converted = append(converted, current)
+			current = ""
+			continue
+		}
+
+		current += " " + line
+	}
+
+	return converted
+}