Feature Request: Multi-reporter aggregation: combine multiple test formats in a single run

[Michealjunior]

Summary
dorny/test-reporter currently assumes that all matched result files share the same format and uses a single reporter input. This makes it hard to use in polyglot repositories where multiple testing frameworks and formats run in the same workflow. Allowing one action invocation to aggregate multiple result formats into a single report would improve usability and reduce workflow duplication.

Describe The Problem

Today the action is configured with a single reporter value and a single path set. All matched files must use that same format, as documented in the README. In multi-language repos, users either have to run separate
test-reporter
steps per framework or normalize all outputs to one format. This increases workflow complexity and can produce multiple disjoint reports instead of one coherent view of test health.

Proposed solution

Introduce first-class support for aggregating multiple test formats in a single
test-reporter run. Users should be able to associate distinct path patterns with specific supported formats, and have the action parse each group with the appropriate parser and then merge the results. The final summary should show correct global totals across all formats and, ideally, make it clear which suites or files came from which framework, while keeping existing single-reporter usage working as it does today.

Alternatives considered

Keep the current model and require separate
test-reporter
steps per framework, accepting multiple reports instead of a unified view.
Ask users to convert all frameworks into a single common format before invoking
test-reporter, which adds extra tooling and maintenance.
Add only cosmetic labeling per framework without true multi-format parsing, which would not solve the underlying limitation for mixed-format inputs.