Restore README.md from upstream

README.md

+# trivial-package-local-nicknames
+
+This was done so there is a portability library for the PLN API not included in `DEFPACKAGE`.
+
+## Supported implementations
+
+* SBCL
+* CCL
+* ECL
+* Clasp
+* ABCL
+* ACL
+* LispWorks (8.0 or later)
+* CLISP (`ros install clisp-head`, build from [here](https://gitlab.com/gnu-clisp/clisp/-/merge_requests/3), or wait until this branch is merged)
+
+## Tests
+
+`(asdf:test-system :trivial-package-local-nicknames)` runs the test suite formerly known as 
+[package-local-nicknames-tests](https://github.com/phoe/package-local-nicknames-tests/).
+If you need to modify the system to add an extra implementation, then only modify the `DEFPACKAGE`
+form to import the proper symbols from your implementation's extension package. Unless you are 
+adding (implementation-specific) test functionality, do not modify the tests themselves.
+
+## License
+
+Unlicense / Public domain