Update production configurations + README for v2.3

* Refactor production nginx configuration files
* Update README for new networks, SQL, etc.

production/nginx/server-electrs.conf

@@ -0,0 +1,35 @@
+server {
+	listen 127.0.0.1:4000;
+	access_log /dev/null;
+	location / {
+		proxy_pass http://electrs-bitcoin-mainnet;
+	}
+}
+server {
+	listen 127.0.0.1:4001;
+	access_log /dev/null;
+	location / {
+		proxy_pass http://electrs-liquid-mainnet;
+	}
+}
+server {
+	listen 127.0.0.1:4002;
+	access_log /dev/null;
+	location / {
+		proxy_pass http://electrs-bitcoin-testnet;
+	}
+}
+server {
+	listen 127.0.0.1:4003;
+	access_log /dev/null;
+	location / {
+		proxy_pass http://electrs-bitcoin-signet;
+	}
+}
+server {
+	listen 127.0.0.1:4004;
+	access_log /dev/null;
+	location / {
+		proxy_pass http://electrs-liquid-testnet;
+	}
+}