add releasing doc

Signed-off-by: Ciro S. Costa <utxobr@protonmail.com>

RELEASING.md

@@ -0,0 +1,33 @@
+# releasing
+
+1. build the container images
+
+```
+make images
+```
+
+2. create a final commit with the images checked out
+
+```
+git add --all .
+git commit # bla bla
+```
+
+3. create a new signed tag
+
+```
+git tag -s $version
+```
+
+4. build the release binaries
+
+```
+goreleaser release --rm-dist
+```
+
+5. sign the checksums
+
+```
+export GPG_TTY=$(tty)
+gpg --clearsign ./dist/checksums.txt
+```