add jvm command display file descriptor count

site/src/site/sphinx/en/jvm.md

@@ -87,6 +87,11 @@ $ jvm
                       PEAK-COUNT     18
                       STARTED-COUNT  19
                       DEADLOCK-COUNT  0
+                      
+ FILE-DESCRIPTOR
+ 
+                      MAX-FILE-DESCRIPTOR-COUNT  10240
+                      OPEN-FILE-DESCRIPTOR-COUNT 648
 Affect cost in 2 ms.
 ```
 
@@ -97,3 +102,9 @@ Affect cost in 2 ms.
 * PEAK-COUNT: the maximum count of the live threads since JVM starts
 * STARTED-COUNT: the total count of the created threads since JVM starts
 * DEADLOCK-COUNT: the count of deadlock threads 
+
+
+### fileDescriptor-related
+
+* MAX-FILE-DESCRIPTOR-COUNT：the count of max file descriptor JVM process can open
+* OPEN-FILE-DESCRIPTOR-COUNT：the current count of file descriptor JVM process open

site/src/site/sphinx/jvm.md

@@ -87,6 +87,11 @@ $ jvm
                       PEAK-COUNT     18
                       STARTED-COUNT  19
                       DEADLOCK-COUNT  0
+
+ FILE-DESCRIPTOR
+ 
+                      MAX-FILE-DESCRIPTOR-COUNT  10240
+                      OPEN-FILE-DESCRIPTOR-COUNT 648
                       
 Affect cost in 2 ms.
 ```
@@ -96,5 +101,10 @@ Affect cost in 2 ms.
 * COUNT: JVM当前活跃的线程数
 * DAEMON-COUNT: JVM当前活跃的守护线程数
 * PEAK-COUNT: 从JVM启动开始曾经活着的最大线程数
-* STARTED-COUNT: 从jvm启动开始总共启动过的线程次数
-* DEADLOCK-COUNT: JVM当前死锁的线程数
+* STARTED-COUNT: 从JVM启动开始总共启动过的线程次数
+* DEADLOCK-COUNT: JVM当前死锁的线程数
+
+### 文件描述符相关
+
+* MAX-FILE-DESCRIPTOR-COUNT：JVM进程最大可以打开的文件描述符数
+* OPEN-FILE-DESCRIPTOR-COUNT：JVM当前打开的文件描述符数