CI: add test/lint/coverage/release workflows (+ optional Pages coverage)

[ritesh006]

Adds a small set of GitHub Actions for the C/Autotools build:

• test.yaml — configure/make (runs a quick smoke of ./axel)
• lint.yaml — clang-format + cppcheck
• coverage-pages.yaml — build with --coverage, run, generate LCOV HTML;
  publish to Pages only on upstream master and only if enabled
• release-packaging.yaml — release build + upload artifact
• changelog.yaml — git-cliff on tag pushes

Notes:

• Installs needed build deps; ensures Autoconf 2.72.
• No source changes.

Enable Pages (maintainers only, optional):

1. Settings → Pages → Source: GitHub Actions
2. Settings → Actions → Variables: ENABLE_PAGES_COVERAGE=true

Then pushes to master will publish LCOV to:
https://axel-download-accelerator.github.io/axel/

Fixes: #445
Ref: #444

[ritesh006]

Ready For Review

[ritesh006]

Hi @ismaell can you please assign me this I want to work on this