update release instructions

RELEASE.md

@@ -20,4 +20,11 @@ Let's say Near releases a new version of nearcore with tag `1.99.0-rc.3`
 ### Notes
 
 * When nearcore releases a new set of release candidates (ie: an `-rc.1` release), this usually involves many more changes than a normal release. Normally, you will need to also update the `rust-toolchain.toml` file to match their version.  
-* If compilation still fails, then you will need to dig deeper into the reasons why. Start with the compilaton errors and work backwards from there.  One thing you might try is to git checkout the original nearcore project at the given tag, and try to compile their project.   
+* If compilation still fails, then you will need to dig deeper into the reasons why. Start with the compilation errors and work backwards from there.  
+* One thing you might try is to git checkout the original nearcore project at the given tag, and try to compile their project. It is not inconceivable that nearcore has a bug in their code that prevents compilation.
+* If nearcore does not compile, you can try to reach out to the Near team on their Discord in the rust-support channel.  They are usually very helpful.
+* We use a multi-stage Dockerfile which compiles the `near-firehose-indexer` app in Docker using the Ubuntu 20.04 image.  One day, this might need to be updated to a more recent version of Ubuntu.  If so, you will need to update the Dockerfile accordingly.  The nearcore project still uses 18.04, so we should be good for a while.
+
+### Then what?
+
+If everything has gone as planned, the Github action will have built a Docker image and notified the cloudbuild-notif Slack channel.  You can now use this image in order to build the bundle image in the `firehose-near` project, using the `Build Docker Image` Github action.