[ADD] electron: add fat client

[VincentSchippefilt]

Add the possibility for people to install o-spreadsheet on their computer as a fat client application. To achieve this, we have:

• packaged spreadsheet into an Electron application.
• updated package.json to reflect the actual run-time dependencies
• added the different electron dependencies and electron-forge build system dependencies
• updated package.json to support the building and packaging of an electron app
• updated the release github action to build and publish the electron app
• added the base page for the electron app itself, with the capabilities to open/save spreadsheet files

Task: 4968109

[robodoo]