Update c8 configuration

Ignore coverage of CJS distribution. It would require its own copy of the unit tests. Since TypeScript injects ES compatibility workarounds, it adds additional unnecessary uncovered logic.

Author: mcaskill

.c8rc.json

@@ -1,4 +1,10 @@
 {
+    "exclude": [
+        "**/*.d.ts",
+        "coverage/**",
+        "dist/cjs/**",
+        "test{,s}/**"
+    ],
     "per-file": true,
     "branches": 80,
     "functions": 80,