Add CONTRIBUTORS generation, and migrate CONTRIBUTORS file to said format.

Makefile

@@ -82,6 +82,13 @@ clean:
 	-$(Q)$(RM) $(OBJ) $(DEP)
 	-$(Q)$(RM) -r bin/
 
+PHONY += CONTRIBUTORS
+CONTRIBUTORS:
+	$(Q)printf "# This file is generated by \`make $@\`, if editing manually, keep it sorted.\n" >CONTRIBUTORS~
+	$(Q)printf "# List of all contributors of the project:\n" >>CONTRIBUTORS~
+	$(Q)git log --format='%aN <%aE>%n%cN <%cE>' | sort -u >>CONTRIBUTORS~
+	$(Q)mv CONTRIBUTORS~ CONTRIBUTORS
+
 # Links together the object files into the final binary.
 bin/$(NAME): $(OBJ) | bin/
 	$(Q)$(call msg,LD,$@)