Run Spider as Docker container

Both amd64 and arm64 editions are available.

On Docker host machine:

Create directory /spider (you're free to use a different directory) to store data, also generate a long random string as secret key (used to encrypt archived email messages and attachments):

WARNING: Keep this secret key file safe.
Email messages and attachments are compressed (in gzip format) and encrypted with this secret key before saving to disk. If this secret key is lost, all archived email messages and attachments are impossible to decrypt and recover.
```
mkdir /spider
cd /spider
LC_CTYPE=C tr -dc [:alnum:] </dev/urandom | head -c 64 > secret.key
chmod 0400 secret.key
```
If you have a purchased ssl cert, please copy the cert and private key files to:
- /spider/cert.pem: the cert file
- /spider/key.pem: the private key
Note: You can request a free ssl cert from Let's Encrypt on Spider web console (Settings -> SSL Cert) to secure SMTP and http connections.
Pull the official image from Docker Hub and launch it:
```
docker run -d \
    --name spider \
    -p 25:25 \
    -p 443:443 \
    -p 8080:8080 \
    -v /spider:/opt/spider \
    iredmail/spider:latest
```
It exposes port 25 for smtp service, 8080 for http service (if ssl cert is unavailable) or 443 for https service (when ssl cert is available) by default.

Spider Email Archiver