chore: replaces c8 with node native coverage (#46)

## Description

- replaces c8 with node 'native' --experimental-test-coverage

## Motivation and Context

c8 in our setup always returned 100% coverage for all things - which
might have to do with an issue in tsx (see [tsx
#433](privatenumber/tsx#433) ), but might just
as well be caused by something unexpectedly breaking in de nodejs / v8
w.r.t. loader coverage.

`--experimental-test-coverage` is not perfect either (i.c.w. tsx it's
unstable on node > 20.12.2, and line numbers are off), but at least the
coverage data we get is more realistic.

## How Has This Been Tested?

- [x] green ci

## Screenshots

```
> tsx --experimental-test-coverage --test-reporter ./tools/dot-with-summary.reporter.js --test src/*.spec.ts src/**/*.spec.ts

.................................................

49 passing (1.420 ms)

=============================== Coverage summary ===============================
Branches     : 97,89 % (93/95) NOK
Functions    : 100 % (38/38)
Lines        : 99,76 % (422/423)
================================================================================

Uncovered lines:
  /Users/sander/prg/js/watskeburt/src/git-primitives.ts:80

Uncovered branches:
  /Users/sander/prg/js/watskeburt/src/git-primitives.ts:79
  /Users/sander/prg/js/watskeburt/src/main.ts:22
```

## Types of changes

- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] Documentation only change
- [ ] Refactor (non-breaking change which fixes an issue without
changing functionality)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [x] Chore

.eslintrc.cjs

@@ -9,7 +9,7 @@ module.exports = {
   },
   overrides: [
     {
-      files: ["**/*.ts"],
+      files: ["**/*.ts", "**/*.js"],
       rules: {
         "unicorn/no-null": "off",
         "unicorn/prefer-spread": "off",

.github/workflows/ci.yml

@@ -29,6 +29,7 @@ jobs:
       matrix:
         node-version:
           - 18.x
+          - 20.12.2
           - 22.x
         platform:
           - ubuntu-latest
@@ -59,16 +60,20 @@ jobs:
         if: matrix.node-version == env.NODE_LATEST
       - run: npm run lint
         if: matrix.node-version == env.NODE_LATEST
-      - run: npm run test:cover
-        if: matrix.node-version == env.NODE_LATEST
+      # - run: npm run test:cover
+      #   if: matrix.node-version == env.NODE_LATEST
       - run: npx tsx --test src/*.spec.ts src/**/*.spec.ts
-        if: matrix.node-version == '18.x'
+        if: matrix.node-version == '18.x' || matrix.node-version == env.NODE_LATEST
       - run: npm run build
       - name: emit coverage results to step summary
-        if: always() && matrix.node-version == env.NODE_LATEST
+        # specifically version 20.12.2 as that's the latest node version where 
+        # coverage reporting (in our setup, with tsx) is still stable.
+        if: always() && matrix.node-version == '20.12.2'
         run: |
           echo '## Code coverage' >> $GITHUB_STEP_SUMMARY
-          npx tsx  tools/istanbul-json-summary-to-markdown.ts < coverage/coverage-summary.json >> $GITHUB_STEP_SUMMARY
+          echo '```' >> $GITHUB_STEP_SUMMARY
+          npx tsx --experimental-test-coverage --test-reporter ./tools/dot-with-summary.reporter.js --test src/*.spec.ts src/**/*.spec.ts >> $GITHUB_STEP_SUMMARY
+          echo '```' >> $GITHUB_STEP_SUMMARY
       - name: emit full depcruise results to step summary
         if: always() && matrix.node-version == env.NODE_LATEST
         run: |