Check for valid app id is missing rules

[A6GibKm]

https://github.com/bilelmoussaoui/flatpak-vscode/blob/master/src/manifestUtils.ts#L91-L132 is

• Not checking for numeric (0..9) characters, its only checking for a-z, A-Z, -, _.
• Not checking if - is only in the last segment.

[SeaDve]

Not checking for numeric (0..9) characters, its only checking for a-z, A-Z, -, _.

I believe it also checks 0..9 characters through isNumber.

[A6GibKm]

Oh you are right, I didn't saw it.

[A6GibKm]

It only leaves us with the - issue, but it might not be part of the spec but an unfortunate consequence of dbus rules.