add readme with cli usage example

src/k2v-client/README.md

@@ -0,0 +1,25 @@
+Example usage:
+```sh
+# all these values can be provided on the cli instead
+export AWS_ACCESS_KEY_ID=GK123456
+export AWS_SECRET_ACCESS_KEY=0123..789
+export AWS_REGION=garage
+export K2V_ENDPOINT=http://172.30.2.1:3903
+export K2V_BUCKET=my-bucket
+
+cargo run --features=cli -- read-range my-partition-key --all
+
+cargo run --features=cli -- insert my-partition-key my-sort-key --text "my string1"
+cargo run --features=cli -- insert my-partition-key my-sort-key --text "my string2"
+cargo run --features=cli -- insert my-partition-key my-sort-key2 --text "my string"
+
+cargo run --features=cli -- read-range my-partition-key --all
+
+causality=$(cargo run --features=cli -- read my-partition-key my-sort-key2 -b | head -n1)
+cargo run --features=cli -- delete my-partition-key my-sort-key2 -c $causality
+
+causality=$(cargo run --features=cli -- read my-partition-key my-sort-key -b | head -n1)
+cargo run --features=cli -- insert my-partition-key my-sort-key --text "my string3" -c $causality
+
+cargo run --features=cli -- read-range my-partition-key --all
+```