Improve tarmkrecovery docs

Add some helper steps on output and what you can actually do with it:

1. Run tarmkrecovery command

nohup java -Xmx2048m -jar oak-run-*.jar tarmkrecovery repository/segmentstore &> tarmkrecovery.log &

2. Take the output of the tarmkrecovery, take the top 10 items output (excluding "Current head revision line") then reverse the order of those and format them to journal.log file format (revision:offset root) and put those values in a fresh journal.log in that format
For example:

6ee64a26-491e-4630-ac2e-bdad1f27e73a:257016 root
5ee64a26-491e-4630-ac2e-bdad1f27e73b:257111 root

3. After setting up the new journal.log then run this command on the segmentstore

nohup java -Xmx2048m -jar oak-run-*.jar check -p repository/segmentstore -d &> check.log &

4. That command will give you output of which of those 10 items in the journal.log are good. Now remove all lines from the journal that come after the last known good revision.