move hacking.md

doc/hacking.md

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+# hacking
+
+## build
+
+Install `Go >= 1.14` and `gcc`. Get the source code:
+
+```sh
+git clone https://github.com/nkanaev/yarr.git
+git clone https://github.com/nkanaev/gofeed.git
+mv gofeed yarr
+cd yarr
+```
+
+Then:
+
+```sh
+# create a binary for the host os
+make build_macos    # -> _output/macos/yarr.app
+make build_linux    # -> _output/linux/yarr
+make build_windows  # -> _output/windows/yarr.exe
+
+# ... or run locally (for testing & hacking)
+go run main.go      # starts a server at http://localhost:7070
+```
+
+## code of conduct
+
+Be excellent to each other. Party on, dudes!