Add missing fuzzer (#2844)

* fuzz: add missing fuzzer by fixing .gitignore adding a negation for caddyfile/ directory

* ci: print fuzzing type for debuggability and traceability

* README: update the Fuzzit badge to point to the correct Caddy server Github organization

caddyconfig/caddyfile/parse_fuzz.go

@@ -0,0 +1,36 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build gofuzz
+// +build gofuzz_libfuzzer
+
+package caddyfile
+
+import (
+	"bytes"
+)
+
+func FuzzParseCaddyfile(data []byte) (score int) {
+	sb, err := Parse("Caddyfile", bytes.NewReader(data))
+	if err != nil {
+		// if both an error is received and some ServerBlocks,
+		// then the parse was able to parse partially. Mark this
+		// result as interesting to push the fuzzer further through the parser.
+		if sb != nil && len(sb) > 0 {
+			return 1
+		}
+		return 0
+	}
+	return 1
+}