child_process: add example for execFileSync method and ref to stdio

Added an example to the execFileSync method. This demonstrates how to
handle exceptions and access the stderr and stdio properties that are
attached to the Error object in a catch block.

Added a link to the detailed stdio section nested under
child_process.spawn() from each child_process sync method option
description.

Fixes: #39306

doc/api/child_process.md

@@ -889,7 +889,8 @@ changes:
   * `input` {string|Buffer|TypedArray|DataView} The value which will be passed
     as stdin to the spawned process. Supplying this value will override
     `stdio[0]`.
-  * `stdio` {string|Array} Child's stdio configuration. `stderr` by default will
+  * `stdio` {string|Array} Child's stdio configuration.
+    See [`child_process.spawn()`][]'s [`stdio`][]. `stderr` by default will
     be output to the parent process' stderr unless `stdio` is specified.
     **Default:** `'pipe'`.
   * `env` {Object} Environment key-value pairs. **Default:** `process.env`.
@@ -930,6 +931,34 @@ If the process times out or has a non-zero exit code, this method will throw an
 function. Any input containing shell metacharacters may be used to trigger
 arbitrary command execution.**
 
+```js
+const { execFileSync } = require('child_process');
+
+try {
+  const stdout = execFileSync('my-script.sh', ['my-arg'], {
+    // Capture stdout and stderr from child process. Overrides the
+    // default behavior of streaming child stderr to the parent stderr
+    stdio: 'pipe',
+
+    // Use utf8 encoding for stdio pipes
+    encoding: 'utf8'
+  });
+
+  console.log(stdout);
+} catch (err) {
+  if (err.code) {
+    // Spawning child process failed
+    console.error(err.code);
+  } else {
+    // Child was spawned but exited with non-zero exit code
+    // Error contains any stdout and stderr from the child
+    const { stdout, stderr } = err;
+
+    console.error({ stdout, stderr });
+  }
+}
+```
+
 ### `child_process.execSync(command[, options])`
 <!-- YAML
 added: v0.11.12
@@ -956,7 +985,8 @@ changes:
   * `input` {string|Buffer|TypedArray|DataView} The value which will be passed
     as stdin to the spawned process. Supplying this value will override
     `stdio[0]`.
-  * `stdio` {string|Array} Child's stdio configuration. `stderr` by default will
+  * `stdio` {string|Array} Child's stdio configuration.
+    See [`child_process.spawn()`][]'s [`stdio`][]. `stderr` by default will
     be output to the parent process' stderr unless `stdio` is specified.
     **Default:** `'pipe'`.
   * `env` {Object} Environment key-value pairs. **Default:** `process.env`.
@@ -1032,6 +1062,7 @@ changes:
   * `argv0` {string} Explicitly set the value of `argv[0]` sent to the child
     process. This will be set to `command` if not specified.
   * `stdio` {string|Array} Child's stdio configuration.
+    See [`child_process.spawn()`][]'s [`stdio`][].
   * `env` {Object} Environment key-value pairs. **Default:** `process.env`.
   * `uid` {number} Sets the user identity of the process (see setuid(2)).
   * `gid` {number} Sets the group identity of the process (see setgid(2)).