Use IPC message to focus on serial plotter window

[AlbyIanna]

Motivation

When serial plotter is already running, trying to open it again should bring the focus to the plotter window. Currently it's not working because running window.focus() raises the a cross-origin error:

Blocked a frame with origin "file://" from accessing a cross-origin frame

Change description

Let the renderer send an IPC message to the backend, which in turn would show the serial plotter window.

Other information

Fixes #1346

Reviewer checklist

• PR addresses a single concern.
• The PR has no duplicates (please search among the Pull Requests before creating one)
• PR title and description are properly filled.
• Docs have been added / updated (for bug fixes / features)

[per1234]

I tested on Windows and Linux and it is working fine.

Thanks Alberto!

[kittaakos]

Thank you!