Add a doc to introduce how to use e2e to test itself #13

	# Licensed to Apache Software Foundation (ASF) under one or more contributor
	# license agreements. See the NOTICE file distributed with
	# this work for additional information regarding copyright
	# ownership. Apache Software Foundation (ASF) licenses this file to you under
	# the Apache License, Version 2.0 (the "License"); you may
	# not use this file except in compliance with the License.
	# You may obtain a copy of the License at
	#
	# http://www.apache.org/licenses/LICENSE-2.0
	#
	# Unless required by applicable law or agreed to in writing,
	# software distributed under the License is distributed on an
	# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
	# KIND, either express or implied. See the License for the
	# specific language governing permissions and limitations
	# under the License.
	#

	name: E2E Test

	concurrency:
	group: ${{ github.workflow }}-${{ github.event.pull_request.number \|\| github.ref }}
	cancel-in-progress: true

	on:
	pull_request:
	branches:
	- main

	jobs:
	build:
	name: E2E Test
	runs-on: ubuntu-latest
	steps:

	- name: Set up Go 1.18
	uses: actions/setup-go@v4
	with:
	go-version: 1.18
	id: go

	- name: Check out code into the Go module directory
	uses: actions/checkout@v3

	- name: Build e2e
	run: make linux

	- name: Run E2E Test
	uses: apache/skywalking-infra-e2e@main
	with:
	e2e-file: ./test/e2e/e2e.yaml

Provide feedback