Support pull_request_target

`pull_request_target` is granted a read/write repository token and runs
in the context of the base of the pull request. It allows to create
workflows that label and comment on pull requests based on the contents
of the event payload. The `get-changed-files` action is useful for some
of those actions and the code works for this case with almost no
modification.

README.md

@@ -4,7 +4,7 @@
 
 # Get All Changed Files
 
-Get all of the files changed/modified in a pull request or push's commits.
+Get all of the files changed/modified in a pull request (`pull_request` or `pull_request_target`) or push's commits.
 You can choose to get all changed files, only added files, only modified files, only removed files, only renamed files, or all added and modified files.
 These outputs are available via the `steps` output context.
 The `steps` output context exposes the output names `all`, `added`, `modified`, `removed`, `renamed`, and `added_modified`.

dist/index.js

@@ -3529,6 +3529,7 @@ function run() {
             let base;
             let head;
             switch (eventName) {
+                case 'pull_request_target':
                 case 'pull_request':
                     base = (_b = (_a = github_1.context.payload.pull_request) === null || _a === void 0 ? void 0 : _a.base) === null || _b === void 0 ? void 0 : _b.sha;
                     head = (_d = (_c = github_1.context.payload.pull_request) === null || _c === void 0 ? void 0 : _c.head) === null || _d === void 0 ? void 0 : _d.sha;

src/main.ts

@@ -26,6 +26,7 @@ async function run(): Promise<void> {
     let head: string | undefined
 
     switch (eventName) {
+      case 'pull_request_target':
       case 'pull_request':
         base = context.payload.pull_request?.base?.sha
         head = context.payload.pull_request?.head?.sha