Include more files in distributions (#4964)

* Include LICENSE files in distributions

* Use pep517 isolated builds

* Update the GH Actions workflow

MANIFEST.in

@@ -0,0 +1,27 @@
+# include license files
+include LICENSE
+recursive-include redbot *.LICENSE
+
+# include locale files
+recursive-include redbot locales/*.po
+
+# include data folders for cogs
+recursive-include redbot/**/data *
+
+# include *.export files from the test fixtures
+recursive-include redbot *.export
+
+# include the py.typed file informing about Red being typed
+recursive-include redbot py.typed
+
+# include *.sql files from postgres driver
+recursive-include redbot/core/drivers/postgres *.sql
+
+# include tests
+graft tests
+
+# include tox configuration
+include tox.ini
+
+# exclude files containing byte-code and compiled libs
+global-exclude *.py[cod]