Pysigma-backend-elasticsearch

- New output format **siem_rule**
- Resulting JSON could be used with Kibana Create Rule API: https://www.elastic.co/guide/en/kibana/8.6/create-rule-api.html
- BUT this is not compatible with the Detection Rule Import Feature: Use **siem_rule_ndjson** instead
- New output format **siem_rule_ndjson**
- Resulting NDJSON could be used with Kibana Security Alert UI to import rule files

- Updated to pySigma 0.8.12
- Fixed and tested escaped `| re` transformation
- Quoting of empty strings
- Changed field with dot value to keyword type

* Updated to pySigma 0.8.
* Field name conditions are now used in pipelines.

Initial release