Described types for argIf (#920)

* Improve types for argIf command

* Bump package version

* Update changelog

Author: localconst

node/CHANGELOG.md

@@ -35,4 +35,8 @@ Backported from ver.`3.4.0`:
 
 ## 4.2.0
 
-- Added unhandledRejection event - [#912](https://github.com/microsoft/azure-pipelines-task-lib/pull/912)
+- Added unhandledRejection event - [#912](https://github.com/microsoft/azure-pipelines-task-lib/pull/912)
+
+## 4.3.0
+
+- Described types for `argIf` - [#920](https://github.com/microsoft/azure-pipelines-task-lib/pull/920)

node/package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "azure-pipelines-task-lib",
-  "version": "4.2.0",
+  "version": "4.3.0",
   "description": "Azure Pipelines Task SDK",
   "main": "./task.js",
   "typings": "./task.d.ts",

node/package.json

@@ -853,7 +853,7 @@ export class ToolRunner extends events.EventEmitter {
      * @param     val     string cmdline or array of strings
      * @returns   ToolRunner
      */
-    public argIf(condition: any, val: any) {
+    public argIf(condition: unknown, val: string | string[]): ToolRunner {
         if (condition) {
             this.arg(val);
         }