Dynamic size of PresenceResponse

[ShortDevelopment]

PresenceResponse is currently using a hard-coded length but is dynamic in size (it contains the device name).

android/lib/ShortDev.Microsoft.ConnectedDevices/Transports/NetworkTransport.cs

Lines 191 to 200 in 4e05e07

	new CommonHeader()
	{
	Type = MessageType.Discovery,
	MessageLength = 97
	}.Write(writer);
	new DiscoveryHeader()
	{
	Type = DiscoveryType.PresenceResponse
	}.Write(writer);
	_presenceResponse.Write(writer);

Therefore this message can't be parsed by other devices and receiving is not possible.

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See nearby-sharing/cli#1 (comment)

@electr1fy0