add npm & git help script

script/git-push-tag.sh

+#!/usr/bin/env bash
+
+[ -z "$!" ] && {
+  echo
+  echo "Usage: git-push-tag.sh <tag>"
+  echo
+  exit 1
+}
+
+NO_HOOK=1 git push origin "$1"

script/npm-set-latest.sh

+#!/usr/bin/env bash
+
+[ -z "$1" ] && {
+  echo
+  echo "Usage: npm-set-latest.sh <wechaty@version>"
+  echo
+  exit 1
+}
+
+npm dist-tag add "$1" latest