feat(config): search .cliff.toml as alternative config file name

[niklasmarderx]

Closes #1446

What this does

When git-cliff searches for a config file it now checks both cliff.toml and .cliff.toml, in that order. Users who keep their configs under dot-prefixed names (a pattern common with .eslintrc, .rustfmt.toml, .prettierrc, etc.) can do the same for git-cliff without any extra flags.

How it works

A new CONFIG_CANDIDATES constant in git-cliff-core lists the names to try:

pub const CONFIG_CANDIDATES: &[&str] = &[DEFAULT_CONFIG, ".cliff.toml"];

All three lookup sites use this slice:

• Config::retrieve_config_path — user-level config directory (and legacy macOS paths)
• parent-directory walk in run_with_changelog_modifier — the ancestor search that finds a cliff.toml in a parent directory

cliff.toml is still index 0, so it always wins over .cliff.toml when both exist. DEFAULT_CONFIG and the --config default are unchanged, so existing setups are completely unaffected.

Testing

Added a unit test to config::test that asserts cliff.toml is first in CONFIG_CANDIDATES and that .cliff.toml is present.

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 47.35%. Comparing base (ee8bfd1) to head (ab9f182).

Files with missing lines	Patch %	Lines
git-cliff-core/src/config.rs	0.00%	6 Missing ⚠️
git-cliff/src/lib.rs	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1482      +/-   ##
==========================================
- Coverage   47.40%   47.35%   -0.04%     
==========================================
  Files          24       24              
  Lines        2129     2131       +2     
==========================================
  Hits         1009     1009              
- Misses       1120     1122       +2     

Flag	Coverage Δ
unit-tests	47.35% <0.00%> (-0.04%)	⬇️

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