feat: allow repositories input to be comma or newline-separated (#169)

Resolves https://github.com/actions/create-github-app-token/issues/106

- Fixes the parsing to cope with whitespace in the input string.
- Allows the input to be comma or newline-separated. (I've done this for
all array-type inputs in my own actions, but I'm happy to remove this if
you only want to support comma-separated.)
- Added tests for parsing comma and newline-separated inputs.

tests/snapshots/index.js.md

@@ -134,6 +134,25 @@ Generated by [AVA](https://avajs.dev).
     ::save-state name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
     ::save-state name=expiresAt::2016-07-11T22:14:10Z`
 
+## main-token-get-owner-set-repo-set-to-many-newline.test.js
+
+> stderr
+
+    ''
+
+> stdout
+
+    `owner and repositories set, creating token for repositories "create-github-app-token,toolkit,checkout" owned by "actions"␊
+    ::add-mask::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
+    ␊
+    ::set-output name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
+    ␊
+    ::set-output name=installation-id::123456␊
+    ␊
+    ::set-output name=app-slug::github-actions␊
+    ::save-state name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
+    ::save-state name=expiresAt::2016-07-11T22:14:10Z`
+
 ## main-token-get-owner-set-repo-set-to-many.test.js
 
 > stderr
@@ -142,7 +161,7 @@ Generated by [AVA](https://avajs.dev).
 
 > stdout
 
-    `owner and repositories set, creating token for repositories "create-github-app-token,toolkit" owned by "actions"␊
+    `owner and repositories set, creating token for repositories "create-github-app-token,toolkit,checkout" owned by "actions"␊
     ::add-mask::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊
     ␊
     ::set-output name=token::ghs_16C7e42F292c6912E7710c838347Ae178B4a␊