docs: point electrum protocol links to spesmilo/electrum-protocol

  The ElectrumX docs (electrumx.readthedocs.io) are frozen ~1.4.2; the
  maintained protocol spec now lives at electrum-protocol.readthedocs.io.
  Update the server.features and status references in README, TODO, and
  the --electrum-hosts help text.

Author: EddieHouston

README.md

@@ -75,7 +75,7 @@ Additional options with the `liquid` feature:
 - `--parent-network <network>` - the parent network this chain is pegged to.
 
 Additional options with the `electrum-discovery` feature:
-- `--electrum-hosts <json>` - a json map of the public hosts where the electrum server is reachable, in the [`server.features` format](https://electrumx.readthedocs.io/en/latest/protocol-methods.html#server.features).
+- `--electrum-hosts <json>` - a json map of the public hosts where the electrum server is reachable, in the [`server.features` format](https://electrum-protocol.readthedocs.io/en/latest/protocol-methods.html#server-features).
 - `--electrum-announce` - announce the electrum server on the electrum p2p server discovery network.
 
 See `$ cargo run --release --bin electrs -- --help` for the full list of options.

TODO.md

@@ -1,7 +1,7 @@
 # Electrum
 
 * Snapshot DB after successful indexing - and run queries on the latest snapshot
-* Update height to -1 for txns with any [unconfirmed input](https://electrumx.readthedocs.io/en/latest/protocol-basics.html#status)
+* Update height to -1 for txns with any [unconfirmed input](https://electrum-protocol.readthedocs.io/en/latest/protocol-basics.html#status)
 
 # Rust
 

src/config.rs

@@ -308,7 +308,7 @@ impl Config {
         let args = args.arg(
                 Arg::with_name("electrum_public_hosts")
                     .long("electrum-public-hosts")
-                    .help("A dictionary of hosts where the Electrum server can be reached at. Required to enable server discovery. See https://electrumx.readthedocs.io/en/latest/protocol-methods.html#server-features")
+                    .help("A dictionary of hosts where the Electrum server can be reached at. Required to enable server discovery. See https://electrum-protocol.readthedocs.io/en/latest/protocol-methods.html#server-features")
                     .takes_value(true)
             ).arg(
                 Arg::with_name("electrum_announce")