[Feature Request] Keybindings depending on the filetype

Keybindings depending on the filetype to have build actions and quickfix plugin work together nicely

Depending on the file type, it might be better to bind the same key to a different command.
I.e with quickfix, depending on the filetype the user might want to execute a different command.
I know about chaining commands with ,, |, &` but that's not the same thing.
The snippet below raises some error when running micro

"*.cs": {
    "F5": "command:fexec dotnet build",
    "Shift-F5": "command:fexec dotnet test",
    },
"*.zig": {
    "F5": "command:fexec zig build",
    "F7": "command:fexec zig ast-check {f}",
    "Shift-F5": "command:fexec zig test {f}",
},

Error

Micro encountered an error: runtime.errorString runtime error: invalid memory address or nil pointer dereference
/usr/lib/golang/src/runtime/panic.go:212 (0x55f1979d3273)
/usr/lib/golang/src/runtime/panic.go:211 (0x55f1979d30f3)
/builddir/build/BUILD/micro-2.0.8/_build/src/github.com/zyedidia/micro/internal/action/bindings.go:88 (0x55f197ed9cbf)
/builddir/build/BUILD/micro-2.0.8/_build/src/github.com/zyedidia/micro/internal/action/bindings.go:70 (0x55f197ed96d7)
/builddir/build/BUILD/micro-2.0.8/_build/src/github.com/zyedidia/micro/cmd/micro/micro.go:318 (0x55f197f15eea)
/usr/lib/golang/src/runtime/proc.go:204 (0x55f1979bfbe9)
/usr/lib/golang/src/runtime/asm_amd64.s:1374 (0x55f1979f34a1)

Reproduce the filetype-specific keybinding configuration and inspect the panic path in internal/action/bindings.go, starting from the call in cmd/micro/micro.go. Determine the intended handling for bindings that vary by filetype; done means the shown configuration loads without a nil-pointer error and the requested commands can be bound per filetype.