feat: refactor yasnippet

Put snippets in standard path

snippets/c-mode/fori

@@ -0,0 +1,8 @@
+# -*- mode: snippet -*-
+# name: for with loop variable
+# key: fori
+# --
+
+for (${1:size_t i = 0}; ${2:i < N}; ${3:++i}) {
+    $0
+}

snippets/c-mode/header

@@ -0,0 +1,10 @@
+#name : #ifndef XXX; #define XXX; #endif
+# key: header
+# --
+
+#ifndef ${1:_`(upcase (file-name-nondirectory (file-name-sans-extension (or (buffer-file-name) ""))))`_H_}
+#define $1
+
+$0
+
+#endif /* $1 */