Add full CI workflow for Nimcheck with lint, test matrix across Nim versions, build, and coverage jobs. Introduce workflow_dispatch trigger, concurrency control, and shared environment variable for Nim version. Enhance job documentation with detailed comments explaining pipeline structure and purpose.
Rename the entire project from "Validatrix" to "Nimcheck" in README.md, Makefile, LESSONS_LEARNED.md, and all source references; add initial Gitea CI workflow with lint, test, and build jobs for Nim 2.0.0; expand .gitignore with comprehensive patterns for Nim, Python, editor, environment, and temporary files; add CONTRIBUTING.md and LICENSE (MIT) files to establish project governance and licensing.
