[doc] update documentation of CLI counters command (#3695)

src/cli/README.md

@@ -17,7 +17,7 @@ OpenThread test scripts use the CLI to execute test cases.
 * [coaps](#coaps-start-checkpeercert)
 * [commissioner](#commissioner-start-provisioningurl)
 * [contextreusedelay](#contextreusedelay)
-* [counter](#counter)
+* [counters](#counters)
 * [dataset](#dataset-help)
 * [delaytimermin](#delaytimermin)
 * [discover](#discover-channel)
@@ -493,22 +493,23 @@ Set the CONTEXT_ID_REUSE_DELAY value.
 Done
 ```
 
-### counter
+### counters
 
 Get the supported counter names.
 
 ```bash
->counter
+>counters
 mac
+mle
 Done
 ```
 
-### counter \<countername\>
+### counters \<countername\>
 
 Get the counter value.
 
 ```bash
->counter mac
+> counters mac
 TxTotal: 10
     TxUnicast: 3
     TxBroadcast: 7
@@ -522,6 +523,7 @@ TxTotal: 10
     TxOther: 0
     TxRetry: 0
     TxErrCca: 0
+    TxErrBusyChannel: 0
 RxTotal: 2
     RxUnicast: 1
     RxBroadcast: 1
@@ -539,6 +541,18 @@ RxTotal: 2
     RxErrSec: 0
     RxErrFcs: 0
     RxErrOther: 0
+Done
+> counters mle
+Role Disabled: 0
+Role Detached: 1
+Role Child: 0
+Role Router: 0
+Role Leader: 1
+Attach Attempts: 1
+Partition Id Changes: 1
+Better Partition Attach Attempts: 0
+Parent Changes: 0
+Done
 ```
 
 ### dataset