Enhance the README a lot

This change is huge, therefore I only sum up the most important changes:
* Improve spelling
* Reduce ambiguity
* Use OpenTofu instead of Terraform
* Document missing tags for Ansible
* Provide example-configuration
* Fix confusion between dotenv and direnv, I use direnv!
* Add section about required software
* Many spelling mistakes

.envrc.tpl

@@ -0,0 +1,6 @@
+#!/bin/bash
+# backblaze keyId
+export AWS_ACCESS_KEY_ID="YOUR_KEY_ID"
+# backblaze applicationKey
+export AWS_SECRET_ACCESS_KEY="YOUR_APPLICATION_KEY"
+