docs: update readme

README.md

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-a webapp and server that monitors bluesky's jetsream and counts how many times different types of records are created or deleted. it shows you which collections (like posts, likes, follows, etc.) are most active on the network.
+a webapp and server that monitors the jetstream and tracks the different lexicons as they are created or deleted.
+it shows you which collections are most active on the network.
 
 for backend it uses rust with fjall as db, the frontend is built with sveltekit.