doc: add ALS metadata-exchange blog and polish E2E doc (#6417)

README.md

@@ -53,6 +53,7 @@ for better performance. Read [the paper of STAM](https://wu-sheng.github.io/STAM
 - [The paper of STAM](https://wu-sheng.github.io/STAM/), Streaming Topology Analysis Method.
 - [Blog](https://skywalking.apache.org/blog/2020-04-13-apache-skywalking-profiling/) about Use Profiling to Fix the Blind Spot of Distributed Tracing
 - [Blog](https://skywalking.apache.org/blog/2020-12-03-obs-service-mesh-with-sw-and-als/) about observing Istio + Envoy service mesh with ALS solution.
+- [Blog](https://skywalking.apache.org/blog/obs-service-mesh-vm-with-sw-and-als/) about observing Istio + Envoy service mesh with ALS Metadata-Exchange mechanism (in VMs and / or Kubernetes).
 
 NOTICE, SkyWalking 8.0+ uses [v3 protocols](docs/en/protocols/README.md). They are incompatible with previous releases.
 

docs/en/guides/README.md

@@ -58,6 +58,11 @@ The e2e test involves some/all of the OAP server, storage, coordinator, webapp,
 besides, there is a test controller(JUnit test) running outside of the container that sends traffics to the instrumented service,
 and then verifies the corresponding results after those requests, by GraphQL API of the SkyWalking Web App.
 
+Before all following steps, please set the SkyWalking version `sw.version` in the [pom.xml](../../../test/e2e/pom.xml)
+so that you can build it in your local IDE, but please make sure not to check this change into the codebase. However, if
+you prefer to build it in command line interface with `./mvnw`, you can simply use property `-Dsw.version=x.y.z` without
+modifying the pom.xml.
+
 #### Writing E2E Cases
 
 - Set up environment in IntelliJ IDEA

docs/en/setup/envoy/als_setting.md

@@ -86,3 +86,4 @@ The [blog](https://skywalking.apache.org/blog/2020-12-03-obs-service-mesh-with-s
 this analyzer requires Istio to enable the metadata exchange plugin (you can enable it by `--set values.telemetry.v2.enabled=true`,
 or if you're using Istio 1.7+ and installing it with profile `demo`/`preview`, it should be enabled then).
 
+The [blog](https://skywalking.apache.org/blog/obs-service-mesh-vm-with-sw-and-als/) illustrates the detail of how it works, and a step-by-step tutorial to apply it into the [Online Boutique](https://github.com/GoogleCloudPlatform/microservices-demo) system.