Sign PuppeteerSharp.dll with private key (hardkoded#1693)

* Sign PuppeteerSharp.dll with private key

Fixes hardkoded#1691

* Remove public.snk, and use keypair.snk instead

* Make assembly version consistent with package version

* Raise version to 4.0.0

v3.0.0 (hardkoded#1653)

* v3.0.0

* Update libraries

* Fix signed test on net48

version 2.0.4 (hardkoded#1525)

v2.0.3 doc (hardkoded#1460)

v2.0.2 (hardkoded#1443)

Publish v2.0.1 (hardkoded#1374)

v2.0 (hardkoded#1328)

Version 1.20 (hardkoded#1293)

v1.19 (hardkoded#1245)

Fix typo (hardkoded#1213)