docs: unify code and shell cmd blocks

docs/etcd.md

@@ -14,8 +14,8 @@ on bitcoin mainnet.
 
 To create a dev build of LND with etcd support use the following command:
 
-```
-make tags="kvdb_etcd"
+```shell
+⛰  make tags="kvdb_etcd"
 ```
 
 The important tag is the `kvdb_etcd`, without which the binary is built without
@@ -29,8 +29,8 @@ directory.
 
 To start your local etcd instance for testing run:
 
-```
-./etcd \
+```shell
+⛰  ./etcd \
     --auto-tls \
     --advertise-client-urls=https://127.0.0.1:2379 \
     --listen-client-urls=https://0.0.0.0:2379 \
@@ -51,8 +51,8 @@ through command line flags or in `lnd.conf`.
 
 Sample command line:
 
-```
-./lnd-debug \
+```shell
+⛰  ./lnd-debug \
     --db.backend=etcd \
     --db.etcd.host=127.0.0.1:2379 \
     --db.etcd.certfile=/home/user/etcd/bin/default.etcd/fixtures/client/cert.pem \
@@ -62,7 +62,7 @@ Sample command line:
 
 Sample `lnd.conf` (with other setting omitted):
 
-```
+```text
 [db]
 backend=etcd
 etcd.host=127.0.0.1:2379