Add support of RESP3 attribute type

Currently, Redis DEBUG PROTOCOL 'attrib' command will return an
attribute type, but hiredis doesn't support it yet. So it got the
protocol type error:

```
127.0.0.1:6379>  DEBUG PROTOCOL attrib
Error: Protocol error, got "|" as reply type byte
```

After apply this PR, it should reply:

```
127.0.0.1:6379> DEBUG PROTOCOL attrib
1# "key-popularity"
1# 1) "key:123"
   2) (integer) 90
```

1 files changed, 6 insertions, 1 deletions

diff --git a/read.c b/read.c
index 9c8f869..fa40e61 100644
--- a/read.c
+++ b/read.c
@@ -250,6 +250,7 @@ static void moveToNextTask(redisReader *r) {
         prv = r->task[r->ridx-1];
         assert(prv->type == REDIS_REPLY_ARRAY ||
                prv->type == REDIS_REPLY_MAP ||
+               prv->type == REDIS_REPLY_ATTR ||
                prv->type == REDIS_REPLY_SET ||
                prv->type == REDIS_REPLY_PUSH);
         if (cur->idx == prv->elements-1) {
@@ -534,7 +535,7 @@ static int processAggregateItem(redisReader *r) {
 
             moveToNextTask(r);
         } else {
-            if (cur->type == REDIS_REPLY_MAP) elements *= 2;
+            if (cur->type == REDIS_REPLY_MAP || cur->type == REDIS_REPLY_ATTR) elements *= 2;
 
             if (r->fn && r->fn->createArray)
                 obj = r->fn->createArray(cur,elements);
@@ -602,6 +603,9 @@ static int processItem(redisReader *r) {
             case '%':
                 cur->type = REDIS_REPLY_MAP;
                 break;
+            case '|':
+                cur->type = REDIS_REPLY_ATTR;
+                break;
             case '~':
                 cur->type = REDIS_REPLY_SET;
                 break;
@@ -642,6 +646,7 @@ static int processItem(redisReader *r) {
         return processBulkItem(r);
     case REDIS_REPLY_ARRAY:
     case REDIS_REPLY_MAP:
+	case REDIS_REPLY_ATTR:
     case REDIS_REPLY_SET:
     case REDIS_REPLY_PUSH:
         return processAggregateItem(r);