[Feature]: Configurable export output format

[olegshulyakov]

Prerequisites

• I am running the latest code. Mention the version if possible as well.
• I carefully followed the README.md.
• I searched using keywords relevant to my issue to make sure that I am creating a new issue that is not already open (or closed).

Description

Make a configurable parameter for message export format.

Motivation

JSON format is not very human readable, consider to use YAML or TOML.

Proposed Solution

1. Add parameter in Settings.
2. Use parameter on Export action.

Alternatives

No response

Additional Context

No response

[olegshulyakov]

Postponed after #6 implementation.