Add sentrum bonus guide

[sommerfelddev]

What

A Bonus Guide for sentrum: a daemon that sends notifications for new transactions in your watch-only wallets

Why

Monitoring your wallets in a safe way is important and a daemon running inside your node connected to your own electrum server is the ideal way to do it.

How

Adapting the project's README instructions to raspibolt

Scope

• [ ] significant change to core configuration
• [x] independent bonus guide
• [ ] simple bug fix

Fixes # (link issue)

Test & maintenance

How can the changes be tested?

I'm the tool author so I tested it myself everyday

Is there ongoing maintenance effort?

I'm maintaining the tool

If this is a bonus guide: are you willing to update it from time to time?

Yes

Animated GIF (optional)

Add some snazz if you feel like it :)

[twofaktor]

Hello, this is an interesting tool, but the existing format of the RaspiBolt guide and builder is not compatible with MiniBolt anymore because MiniBolt uses Gitbook and RaspiBolt Github pages, they also use different architectures.

I will reserve this PR as a reference and close it for building later using Gitbook. Thanks for your contribution