docs: Add UPDATING.md with instructions on merging from upstream.

UPDATING.md

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+# Updating from upstream
+
+We'll use the upstream version v1.14.10 as an example.
+
+## Add origin
+
+```
+git add remote upstream git@github.com:ethereum/go-ethereum.git
+```
+
+## Find version to upgrade to
+
+Go to https://github.com/ethereum/go-ethereum/releases and find the tag you want to update to
+
+## Check out latest bn/geth and upstream/geth
+
+```
+git fetch origin
+git fetch upstream
+git checkout mempool-feed-stage
+git pull origin mempool-feed-stage
+```
+
+## Create working branch
+
+```
+git checkout -b upgrade/v1.14.10
+```
+
+## Merge
+
+```
+git merge v1.14.10
+```
+
+## Fix conflicts
+
+No systemic way to handle this. Use `git status` and `git diff` to find the conflicts and compare against upstream.
+
+`git commit` to finish after all conflicts are fixed.
+
+## Check
+
+`make geth` to build and ensure there are no compilation errors. Fix any issues and repeat until it builds.
+
+## Push / test
+
+Push the branch to Github and make a Pull Request. Let the tests run. Fix any issues and repeat until they pass.
+
+## Stream API check
+
+
+###
+SSH into a staging geth node with 8546 forwarded to your local machein.
+
+Example: `ssh -L 8546:0.0.0.0:8546 10.0.1.29`
+
+### Update Geth
+
+```
+sudo su ubuntu
+cd ~/go-ethereum
+git fetch origin
+git checkout origin/upgrade/v1.14.10
+export PATH=/opt/go/1.21.0/bin:$PATH
+make geth
+sudo systemctl stop geth && sudo cp ./build/bin/geth /usr/local/bin/geth && sudo systemctl start geth
+```
+
+Make sure it's running with `sudo journalctl -u geth.service -f`
+
+###
+Connect to the trace stream from your local machine using wscat:
+
+```
+wscat -w 10 -c http://localhost:8546 -x '{"id":1,"jsonrpc":"2.0","method":"eth_subscribe","params":["newPendingTransactionsWithTrace"]}'
+```
+
+## Merge Pull Request + Tag + Release
+
+Now that all testing is done you can merge and close the Pull Request. Now pull the latest `mempool-feed-stage` and tag it with the upstream tag plus `-1`. Any updates based on this version will increment this suffix.
+
+```
+git checkout mempool-feed-stage
+git fetch origin
+git pull origin mempool-feed-stage
+git tag v1.14.10-1
+git push origin v1.14.10-1
+```
+
+Now to go https://github.com/blocknative/go-ethereum/releases and create a new release with the tag.