test: increase coverage for readline

1. test call readline.Interface without new should return instance
Refs: https://coverage.nodejs.org/coverage-f7dd330ba0e7bfa9/lib/readline.js.html#L101

2. test keypress ctrl + c should close readline interface
Refs: https://coverage.nodejs.org/coverage-f7dd330ba0e7bfa9/lib/readline.js.html#L891

test/parallel/test-readline-interface.js

@@ -63,6 +63,12 @@ function assertCursorRowsAndCols(rli, rows, cols) {
   assert.strictEqual(cursorPos.cols, cols);
 }
 
+{
+  const input = new FakeInput();
+  const rl = readline.Interface({ input });
+  assert(rl instanceof readline.Interface);
+}
+
 [
   undefined,
   50,
@@ -657,6 +663,13 @@ function assertCursorRowsAndCols(rli, rows, cols) {
   rli.close();
 }
 
+// Close readline interface
+{
+  const [rli, fi] = getInterface({ terminal: true, prompt: '' });
+  fi.emit('keypress', '.', { ctrl: true, name: 'c' });
+  assert(rli.closed);
+}
+
 // Multi-line input cursor position
 {
   const [rli, fi] = getInterface({ terminal: true, prompt: '' });