feat(utils, templates, docs): file-based templates + stronger README

templates/problem/go/main.go.tmpl

@@ -0,0 +1,18 @@
+// LeetCode {{NUMBER}}: {{NAME_TITLE}}
+// 難度: {{DIFFICULTY}}
+// 日期: {{DATE}}
+
+package main
+
+import "fmt"
+
+// TODO: 根據題意調整簽名
+func solve(nums []int) int {
+    return 0
+}
+
+func main() {
+    fmt.Printf("Hello LeetCode {{NUMBER}}!\n")
+    // TODO: 可加入簡單測試
+}
+