Add RELEASE.md to describe the release process

RELEASE.md

@@ -0,0 +1,25 @@
+# How to make a release
+
+Check master is building properly
+
+Check on master
+
+    git checkout master
+
+Tag
+
+    git tag -s v2.0.x -m "Release v2.0.x"
+
+Push the signed tag
+
+    git push --follow-tags
+
+Go to https://github.com/ncw/swift/tags and check the tag is there.
+
+From there click create a release.
+
+Use the generate release notes button and publish.
+
+Possibly use this instead?
+
+    gh release create v2.0.x --generate-notes