implement ipc for file selection

[achou11]

Related to #55

Sets up the mechanisms for initiating the selection of a file in the filesystem from the renderer side and retrieving the full path to the selected file. Having this will enable features such as importing a project config file or custom map file.

This PR introduces the following:

• IPC handler on the main window for summoning the open file dialog and returning the full path to the selected file (or undefined if no file is selected). Multi-file support was considered but we don't have an immediate need for it, so opted to refrain from including in this implementation.

• new renderer-available "runtime" method selectFile(extensionFilters) which sends the relevant IPC and waits for the result.

• mutation hook useSelectProjectConfigFile() which is unused in this PR, but will help feat: import config #55. Example usage could look like the following:

  onClick={() => {
      selectConfigFile.mutate(undefined, {
  	    onSuccess: (filePath) => {
  		    if (filePath) {
  			    // Do something with selected file...
  		    } else {
  			    // No file selected due to dialog cancellation
  		    }
  	    },
  	    onError: (error) => {
  		    // Handle error...
  	    },
      })
  }}

[cimigree]

Looks great. Thanks for doing this. I tested in the electron console and it worked as expected.