Replace nyc with c8

.gitignore

@@ -1,6 +1,5 @@
 .DS_Store
 *.log
-.nyc_output/
 coverage/
 node_modules/
 yarn.lock

index.js

@@ -10,7 +10,8 @@ module.exports = footnotes
 function footnotes(options) {
   var data = this.data()
 
-  /* istanbul ignore next - old remark. */
+  // Old remark.
+  /* c8 ignore next 14 */
   if (
     !warningIssued &&
     ((this.Parser &&
@@ -31,7 +32,8 @@ function footnotes(options) {
   add('toMarkdownExtensions', toMarkdown)
 
   function add(field, value) {
-    /* istanbul ignore if - other extensions. */
+    // Other extensions.
+    /* c8 ignore next */
     if (data[field]) data[field].push(value)
     else data[field] = [value]
   }

package.json

@@ -35,8 +35,8 @@
     "micromark-extension-footnote": "^0.3.0"
   },
   "devDependencies": {
+    "c8": "^7.0.0",
     "dtslint": "^4.0.0",
-    "nyc": "^15.0.0",
     "prettier": "^2.0.0",
     "rehype-format": "^3.0.0",
     "rehype-stringify": "^8.0.0",
@@ -54,17 +54,11 @@
   },
   "scripts": {
     "format": "remark . -qfo && prettier . -w --loglevel warn && xo --fix",
-    "test-api": "node test",
-    "test-coverage": "nyc --reporter lcov tape test/index.js",
+    "test-api": "node --conditions development test/index.js",
+    "test-coverage": "c8 --check-coverage --branches 100 --functions 100 --lines 100 --statements 100 --reporter lcov npm run test-api",
     "test-types": "dtslint types",
     "test": "npm run format && npm run test-coverage && npm run test-types"
   },
-  "nyc": {
-    "check-coverage": true,
-    "lines": 100,
-    "functions": 100,
-    "branches": 100
-  },
   "prettier": {
     "tabWidth": 2,
     "useTabs": false,