feat: add general read_network function

src/io/read_network.jl

@@ -0,0 +1,8 @@
+function read_network(path::AbstractString)
+    ext = splitext(path)
+    if ext == ".m"
+        return read_matpower(path)
+    elseif ext == ".raw"
+        return read_rawgo(path)
+    end
+end