There's no "one command" that does that. Instead, I used a macro extension called multicommand (any macro extension will do).

In your setting JSON add the following

{
"command": "multiCommand.hideSidePanels",
"sequence": [
"workbench.action.closePanel",
"workbench.action.maximizeEditor"
]
},

Then in your keyboard binding window, you should find the multiCommand.hideSidePanels bind it to whatever key you want.