Add Node.js meta documents

See: nodejs/admin#541
Fixes #312.

CODE_OF_CONDUCT.md

@@ -0,0 +1,7 @@
+# Code of Conduct
+
+Undici is committed to upholding the Node.js Code of Conduct.
+
+The Node.js Code of Conduct document has moved to
+https://github.com/nodejs/admin/blob/master/CODE_OF_CONDUCT.md Please update
+links to this document accordingly.

CONTRIBUTING.md

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+# Developer's Certificate of Origin 1.1
+
+By making a contribution to this project, I certify that:
+
+* (a) The contribution was created in whole or in part by me and I
+ have the right to submit it under the open source license
+ indicated in the file; or
+
+* (b) The contribution is based upon previous work that, to the best
+ of my knowledge, is covered under an appropriate open source
+ license and I have the right under that license to submit that
+ work with modifications, whether created in whole or in part
+ by me, under the same open source license (unless I am
+ permitted to submit under a different license), as indicated
+ in the file; or
+
+* (c) The contribution was provided directly to me by some other
+ person who certified (a), (b) or (c) and I have not modified
+ it.
+
+* (d) I understand and agree that this project and the contribution
+ are public and that a record of the contribution (including all
+ personal information I submit with it, including my sign-off) is
+ maintained indefinitely and may be redistributed consistent with
+ this project or the open source license(s) involved.
+
+## Moderation Policy
+
+The [Node.js Moderation Policy] applies to this project.
+
+[Node.js Moderation Policy]:
+https://github.com/nodejs/admin/blob/master/Moderation-Policy.md

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2018 Matteo Collina
+Copyright (c) Matteo Collina and Undici contributors
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal