Add abs path option for input file

[khoitx-ugaming]

Add an option to allow absolute path for input file

protoc -I /usr/local/include \
       	-I ./pkg \
       	--gotag_out=outabsdir="/absolutePath:/absolutePath" example/example.proto

this will attempt to execute the tag replacement in /absolutePath/example_go_package/example.proto.go, instead ./go_package/example.proto.go

[mesmerx]

whats is the use case for this absolute path exactly, what you today cannot achieve?