Port ESP8266 DNSServer (#779)

Add a simple DNS server for AP mode
Point DHCP server DNS entry to GW for DNSServer

Author: earlephilhower

libraries/DNSServer/keywords.txt

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+#######################################
+# Syntax Coloring Map For DNSServer
+#######################################
+
+#######################################
+# Library (KEYWORD3)
+#######################################
+
+DNSServer	KEYWORD3		RESERVED_WORD
+
+#######################################
+# Datatypes (KEYWORD1)
+#######################################
+
+DNSReplyCode	KEYWORD1		DATA_TYPE
+DNSHeader	KEYWORD1		DATA_TYPE
+DNSServer	KEYWORD1		DATA_TYPE
+
+#######################################
+# Methods and Functions (KEYWORD2)
+#######################################
+
+processNextRequest	KEYWORD2
+setErrorReplyCode	KEYWORD2
+setTTL	KEYWORD2
+start	KEYWORD2
+stop	KEYWORD2
+
+#######################################
+# Constants (LITERAL1)
+#######################################
+
+DNS_QR_QUERY	LITERAL1		RESERVED_WORD_2
+DNS_QR_RESPONSE	LITERAL1		RESERVED_WORD_2
+DNS_OPCODE_QUERY	LITERAL1		RESERVED_WORD_2
+MAX_DNSNAME_LENGTH	LITERAL1		RESERVED_WORD_2
+NoError	LITERAL1		RESERVED_WORD_2
+FormError	LITERAL1		RESERVED_WORD_2
+ServerFailure	LITERAL1		RESERVED_WORD_2
+NonExistentDomain	LITERAL1		RESERVED_WORD_2
+NotImplemented	LITERAL1		RESERVED_WORD_2
+Refused	LITERAL1		RESERVED_WORD_2
+YXDomain	LITERAL1		RESERVED_WORD_2
+YXRRSet	LITERAL1		RESERVED_WORD_2
+NXRRSet	LITERAL1		RESERVED_WORD_2

libraries/DNSServer/library.properties

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+name=DNSServer
+version=1.1.1
+author=Kristijan Novoselić
+maintainer=Earle F. Philhower, III <earlephilhower@yahoo.com>
+sentence=A simple DNS server for ESP8266, ported to the Pico
+paragraph=This library implements a simple DNS server.
+category=Communication
+url=
+architectures=rp2040
+dot_a_linkage=true