doc: mark NAPI_AUTO_LENGTH as code

Backport-PR-URL: #19447
PR-URL: #18697
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

doc/api/n-api.md

@@ -552,10 +552,10 @@ NAPI_NO_RETURN void napi_fatal_error(const char* location,
 
 - `[in] location`: Optional location at which the error occurred.
 - `[in] location_len`: The length of the location in bytes, or
-NAPI_AUTO_LENGTH if it is null-terminated.
+`NAPI_AUTO_LENGTH` if it is null-terminated.
 - `[in] message`: The message associated with the error.
 - `[in] message_len`: The length of the message in bytes, or
-NAPI_AUTO_LENGTH if it is
+`NAPI_AUTO_LENGTH` if it is
 null-terminated.
 
 The function call does not return, the process will be terminated.
@@ -1258,7 +1258,7 @@ napi_status napi_create_function(napi_env env,
 - `[in] utf8name`: A string representing the name of the function encoded as
 UTF8.
 - `[in] length`: The length of the utf8name in bytes, or
-NAPI_AUTO_LENGTH if it is null-terminated.
+`NAPI_AUTO_LENGTH` if it is null-terminated.
 - `[in] cb`: A function pointer to the native function to be invoked when the
 created function is invoked from JavaScript.
 - `[in] data`: Optional arbitrary context data to be passed into the native
@@ -1491,7 +1491,7 @@ napi_status napi_create_string_latin1(napi_env env,
 - `[in] env`: The environment that the API is invoked under.
 - `[in] str`: Character buffer representing a ISO-8859-1-encoded string.
 - `[in] length`: The length of the string in bytes, or
-NAPI_AUTO_LENGTH if it is null-terminated.
+`NAPI_AUTO_LENGTH` if it is null-terminated.
 - `[out] result`: A `napi_value` representing a JavaScript String.
 
 Returns `napi_ok` if the API succeeded.
@@ -1516,7 +1516,7 @@ napi_status napi_create_string_utf16(napi_env env,
 - `[in] env`: The environment that the API is invoked under.
 - `[in] str`: Character buffer representing a UTF16-LE-encoded string.
 - `[in] length`: The length of the string in two-byte code units, or
-NAPI_AUTO_LENGTH if it is null-terminated.
+`NAPI_AUTO_LENGTH` if it is null-terminated.
 - `[out] result`: A `napi_value` representing a JavaScript String.
 
 Returns `napi_ok` if the API succeeded.
@@ -1540,7 +1540,7 @@ napi_status napi_create_string_utf8(napi_env env,
 
 - `[in] env`: The environment that the API is invoked under.
 - `[in] str`: Character buffer representing a UTF8-encoded string.
-- `[in] length`: The length of the string in bytes, or NAPI_AUTO_LENGTH
+- `[in] length`: The length of the string in bytes, or `NAPI_AUTO_LENGTH`
 if it is null-terminated.
 - `[out] result`: A `napi_value` representing a JavaScript String.
 
@@ -3066,7 +3066,7 @@ napi_status napi_define_class(napi_env env,
  - `[in] utf8name`: Name of the JavaScript constructor function; this is
    not required to be the same as the C++ class name, though it is recommended
    for clarity.
- - `[in] length`: The length of the utf8name in bytes, or NAPI_AUTO_LENGTH
+ - `[in] length`: The length of the utf8name in bytes, or `NAPI_AUTO_LENGTH`
 if it is null-terminated.
  - `[in] constructor`: Callback function that handles constructing instances
    of the class. (This should be a static method on the class, not an actual