txoo: connect to vls and cln

- set env var for vls frontend
- set arg for vlsd2
- create txoo-server service
- cln uses http source
- vls fetch public key using curl with retries fail if not set
- update README for vls standalone
Signed-off-by: Lakshya Singh <lakshay.singh1108@gmail.com>

lightningd/entrypoint.sh

@@ -4,6 +4,7 @@ set -e
 cp -u /testnet-config ${LIGHTNINGD_DATA}/testnet-config
 cp -u /regtest-config ${LIGHTNINGD_DATA}/regtest-config
 
+# this is kept for backward compatibility purposes
 export GREENLIGHT_VERSION=$(lightningd --version)
 export VLS_CLN_VERSION=$(lightningd --version)