ffi-napi: First argument to 'Library' can be null (DefinitelyTyped#45109)

Evidence: https://www.npmjs.com/package/ffi-napi#example

Author: cakoose

types/ffi-napi/ffi-napi-tests.ts

@@ -104,3 +104,10 @@ import TArray = require('ref-array-di');
 {
     const refCharArr = TArray('char')([1, 3, 5], 2).ref();
 }
+{
+    // You can also access just functions in the current process by passing a null
+    const current = ffi.Library(null, {
+      atoi: [ 'int', [ 'string' ] ]
+    });
+    current.atoi('1234');
+}

types/ffi-napi/index.d.ts

@@ -20,14 +20,14 @@ export interface Library {
      * @param funcs hash of [retType, [...argType], opts?: {abi?, async?, varargs?}]
      * @param lib hash that will be extended
      */
-    new (libFile: string, funcs?: {[key: string]: any[]}, lib?: object): any;
+    new (libFile: string | null, funcs?: {[key: string]: any[]}, lib?: object): any;
 
     /**
      * @param libFile name of library
      * @param funcs hash of [retType, [...argType], opts?: {abi?, async?, varargs?}]
      * @param lib hash that will be extended
      */
-    (libFile: string, funcs?: {[key: string]: any[]}, lib?: object): any;
+    (libFile: string | null, funcs?: {[key: string]: any[]}, lib?: object): any;
 }
 export const Library: Library;