[feature] add rate limit middleware (#741)

* feat: add rate limit middleware

* chore: update vendor dir

* chore: update readme with new dependency

* chore: add rate limit infos to swagger.md file

* refactor: add ipv6 mask limiter option

Add IPv6 CIDR /64 mask

* refactor: increase rate limit to 1000

Address https://github.com/superseriousbusiness/gotosocial/pull/741#discussion_r945584800

Co-authored-by: tobi <31960611+tsmethurst@users.noreply.github.com>

vendor/github.com/ulule/limiter/v3/internal/bytebuffer/pool.go

@@ -0,0 +1,58 @@
+package bytebuffer
+
+import (
+	"sync"
+	"unsafe"
+)
+
+// ByteBuffer is a wrapper around a slice to reduce memory allocation while handling blob of data.
+type ByteBuffer struct {
+	blob []byte
+}
+
+// New creates a new ByteBuffer instance.
+func New() *ByteBuffer {
+	entry := bufferPool.Get().(*ByteBuffer)
+	entry.blob = entry.blob[:0]
+	return entry
+}
+
+// Bytes returns the content buffer.
+func (buffer *ByteBuffer) Bytes() []byte {
+	return buffer.blob
+}
+
+// String returns the content buffer.
+func (buffer *ByteBuffer) String() string {
+	// Copied from strings.(*Builder).String
+	return *(*string)(unsafe.Pointer(&buffer.blob)) // nolint: gosec
+}
+
+// Concat appends given arguments to blob content
+func (buffer *ByteBuffer) Concat(args ...string) {
+	for i := range args {
+		buffer.blob = append(buffer.blob, args[i]...)
+	}
+}
+
+// Close recycles underlying resources of encoder.
+func (buffer *ByteBuffer) Close() {
+	// Proper usage of a sync.Pool requires each entry to have approximately
+	// the same memory cost. To obtain this property when the stored type
+	// contains a variably-sized buffer, we add a hard limit on the maximum buffer
+	// to place back in the pool.
+	//
+	// See https://golang.org/issue/23199
+	if buffer != nil && cap(buffer.blob) < (1<<16) {
+		bufferPool.Put(buffer)
+	}
+}
+
+// A byte buffer pool to reduce memory allocation pressure.
+var bufferPool = &sync.Pool{
+	New: func() interface{} {
+		return &ByteBuffer{
+			blob: make([]byte, 0, 1024),
+		}
+	},
+}