Add --show-config option

[artem-y]

In this PR:

• added --show-config option which prints out the current config
• when the config file exists but is empty, it won't throw error and will instead show an empty config
• added tests, updated README

[Copilot]

Pull request overview

Adds a --show-config CLI option to print the configuration the tool is using, along with config-loading tweaks and accompanying unit/e2e tests and README updates.

Changes:

• Added --show-config flag to print the current config as formatted JSON.
• Updated config loading/encoding logic and added unit tests for encoding and empty-config-file behavior.
• Added an end-to-end test for --show-config and documented the flag in the README.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
internal/config/config.go	Adds EncodeConfigAtPath and modifies config reading/validation flow (incl. empty-file handling).
internal/config/config_test.go	Updates existing tests for new ReadCommitConfig signature; adds new tests for empty file + encoding behavior.
cmd/commit/main.go	Wires --show-config into the CLI flow and prints config JSON to stdout.
e2e.sh	Adds an e2e test that validates --show-config output formatting/content.
docs/README.md	Documents the new --show-config option.

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