fix: geodata reader for multi-platform compatibility

[rurirei]

this provides a method to oveeride fileReader for specified platform, such as gomobile for android. @Loyalsoldier @xiaokangwang

vfilesystem.NewFileSeeker = func(path string) (io.ReadSeekCloser, error) {
	_, name := filepath.Split(path)
	return gomobileasset.Open(name)
}

[rurirei]

@yuhan6665 may helped for your.

[Loyalsoldier]

其实可以改成 io.ReadSeeker，这样的话，就算是 buffer 或者 []byte 作为实参也可以直接读取并解码。

[rurirei]

the new geodata loader may causes a slow or failed start with core.NewInstance.Start(), i need to try much times (to tap button) to start service. 😕

[Loyalsoldier]

the new geodata loader may causes a slow or failed start with core.NewInstance.Start(), i need to try much times (to tap button) to start service. 😕

Refinements are on the way.