docs(autok3s): update README.md HA section

Signed-off-by: Jason-ZW <zhenyang@rancher.com>

README.md

@@ -50,9 +50,14 @@ sudo autok3s create \
     --master 1
 ```
 
-HA mode need `--master` greater than 1, also need to specify `--datastore` e.g.
+HA(embedded etcd) mode need `--master` at least 3 nodes, e.g.
 ```bash
---master 2 --datastore "mysql://<user>:<password>@tcp(<ip>:<port>)/<db>"
+--master 2"
+```
+
+HA(external database) mode need `--master` greater than 1 node, also need to specify `--datastore` and `--k3s-version`, e.g.
+```bash
+--master 2 --datastore "mysql://<user>:<password>@tcp(<ip>:<port>)/<db>" --k3s-version="v1.18.9-k3s1"
 ```
 
 ### Join K3s Nodes
@@ -80,9 +85,14 @@ sudo autok3s join \
     --worker 1
 ```
 
-HA mode need `--master` greater than 0, also need to specify `--datastore` e.g.
+Join master nodes to (embedded etcd) HA cluster e.g.
+```bash
+--master 2
+```
+
+Join master nodes to (external database) HA cluster, also need to specify `--datastore` and `--k3s-version`, e.g.
 ```bash
---master 1 --datastore "mysql://<user>:<password>@tcp(<ip>:<port>)/<db>"
+--master 2 --datastore "mysql://<user>:<password>@tcp(<ip>:<port>)/<db>" --k3s-version="v1.18.9-k3s1"
 ```
 
 ### Delete K3s Cluster