Support optional chaining via acorn fork (#3582)

* support optional chaining via acorn fork

* fixup test

* fixup dep

* Make acorn a devDependency again

* Modify test to see at least basic tree-shaking works.

* Update dependencies and do not bundle acorn twice

Co-authored-by: Lukas Taegert-Atkinson <lukas.taegert-atkinson@tngtech.com>

LICENSE.md

@@ -28,33 +28,6 @@ The published Rollup artifact additionally contains code with the following lice
 MIT, ISC
 
 # Bundled dependencies:
-## acorn
-License: MIT
-By: Marijn Haverbeke, Ingvar Stepanyan, Adrian Heine
-Repository: https://github.com/acornjs/acorn.git
-
-> Copyright (C) 2012-2018 by various contributors (see AUTHORS)
-> 
-> Permission is hereby granted, free of charge, to any person obtaining a copy
-> of this software and associated documentation files (the "Software"), to deal
-> in the Software without restriction, including without limitation the rights
-> to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-> copies of the Software, and to permit persons to whom the Software is
-> furnished to do so, subject to the following conditions:
-> 
-> The above copyright notice and this permission notice shall be included in
-> all copies or substantial portions of the Software.
-> 
-> THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-> IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-> FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-> AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-> LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-> OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-> THE SOFTWARE.
-
----------------------------------------
-
 ## acorn-class-fields
 License: MIT
 By: Adrian Heine
@@ -343,6 +316,33 @@ Repository: jonschlinkert/fill-range
 
 ---------------------------------------
 
+## fork-acorn-optional-chaining
+License: MIT
+By: Marijn Haverbeke, Ingvar Stepanyan, Adrian Heine
+Repository: https://github.com/acornjs/acorn.git
+
+> Copyright (C) 2012-2018 by various contributors (see AUTHORS)
+> 
+> Permission is hereby granted, free of charge, to any person obtaining a copy
+> of this software and associated documentation files (the "Software"), to deal
+> in the Software without restriction, including without limitation the rights
+> to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+> copies of the Software, and to permit persons to whom the Software is
+> furnished to do so, subject to the following conditions:
+> 
+> The above copyright notice and this permission notice shall be included in
+> all copies or substantial portions of the Software.
+> 
+> THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+> IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+> FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+> AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+> LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+> OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+> THE SOFTWARE.
+
+---------------------------------------
+
 ## glob-parent
 License: ISC
 By: Gulp Team, Elan Shanker, Blaine Bublitz