Loop server regtest documentation is not up to date

Hey,

I couldn't make loopserver work without adding a bitcoind node, but this aspect is not stated on the [documentation](https://github.com/lightninglabs/loop/tree/master/regtest)

Besides, the examples use a old version of LND.

Bonus: Here below you will find some guidelines on how to set up a regtest loop environment with a [Polar Lightning Network](https://lightningpolar.com/). Example polar network file: [regtest.polar.zip](https://github.com/lightninglabs/loop/files/10580893/regtest.polar.zip)

Steps:
1. Set up polar lightning with the file above, also extract this file to a regtest.polar dir
2. Fix loopserver docker images to support bind mounted lnd datadir (from the extracted dir above)
```Dockefile
FROM lightninglabs/loopserver:v0.9.94-beta

COPY regtest.polar/volumes/lnd/alice /root/.lnd

USER root

RUN chmod -R 777 /root/.lnd
RUN chown -R loopserver:loopserver /root/.lnd

USER loopserver
```
3. Launch a loopserver and a loopd(uncomment if you want to use it) with the following docker-compose.yml
````yaml
version: '3'
services:
loopserver:
hostname: loopserver
ports:
- "11009:11009"
extra_hosts:
- "alice:host-gateway"
#image: lightninglabs/loopserver:v0.9.77-beta
build:
context: .
dockerfile: Dockerfile.loopserver
platform: linux/amd64
restart: unless-stopped
networks:
- regtest
command:
- "daemon"
- "--maxamt=5000000"
- "--lnd.host=alice:10001"
- "--lnd.macaroondir=/home/loopserver/.lnd/data/chain/bitcoin/regtest"
- "--lnd.tlspath=/home/loopserver/.lnd/tls.cert"
- "--bitcoin.host=alice:18443"
- "--bitcoin.user=polaruser"
- "--bitcoin.password=polaruser"
- "--bitcoin.httppostmode"
volumes:
- ./regtest.polar/volumes/lnd/alice:/home/loopserver/.lnd

# loopd:
# image: loopd
# extra_hosts:
# - "carol:host-gateway"
# build:
# context: ./loop
# dockerfile: Dockerfile
# restart: unless-stopped
# networks:
# - regtest
# ports:
# - "11010:11010"
# - "8088:8081"
# volumes:
# - "./regtest.polar/volumes/lnd/carol:/root/.lnd"
# - "./loop:/root/.loop"
# command:
# - "loopd"
# - "--network=regtest"
# - "--debuglevel=debug"
# - "--server.host=loopserver:11009"
# - "--server.notls"
# - "--lnd.host=carol:10003"
# - "--lnd.macaroonpath=/root/.lnd/data/chain/bitcoin/regtest/admin.macaroon"
# - "--lnd.tlspath=/root/.lnd/tls.cert"

networks:
regtest:
````