Add new shortcut for those undefined ones

[long-nguyenxuan]

How could I set my own shortcut, eg: ctrl+5 for md-shortcut.toggleStrikethrough? (derive from Excel)
I think there should be some shortcut:

Name	Description	Default key binding
md-shortcut.toggleStrikethrough	Make strikethrough	Ctrl+5 (excel)
md-shortcut.toggleTitleH1	Toggle # H1 title	Ctrl+Alt+1 (word)
md-shortcut.toggleTitleH2	Toggle ## H2 title	Ctrl+Alt+2 (word)
md-shortcut.toggleTitleH3	Toggle ### H3 title	Ctrl+Alt+3 (word)
md-shortcut.toggleTitleH4	Toggle #### H4 title	Ctrl+Alt+4 (word)
md-shortcut.toggleTitleH5	Toggle ##### H5 title	Ctrl+Alt+5 (word)
md-shortcut.toggleTitleH6	Toggle ###### H6 title	Ctrl+Alt+6 (word)
md-shortcut.addTable	Add Tabular values	Ctrl+T (excel)
md-shortcut.addTableWithHeader	Add Tabular values with header	Ctrl+Shift+T

[mdickin]

@long-nguyenxuan see here: https://code.visualstudio.com/docs/getstarted/keybindings#_keyboard-shortcuts-editor

Unfortunately, ctrl+5 would not be a good default shortcut, as VS Code already uses it. However, feel free to use it yourself.