Add new parameter to items to allow the use of Mega Evolution

[Aelysya]

Description

This PR add a new parameter to items that allow to know if possessing this item in the bag allows the player to Mega Evolve its Pokémon

closes #416

Tests to perform

• Opening a project correctly launches the migration
• After the migration, pre-existing mega tools all have the isAllowingMega parameter set to true in their JSON file (Mega Ring, Mega Bracelet, Mega Anchor are example of mega tools)
• The badge Mega Evolution appears in the 'parameters' block of these items in the Database
• Opening the parameters editor correctly shows a new Toggle option to define if the item allows the use of Mega Evolution
• Modifying the toggle value correctly changes the JSON value isAllowingMega

[AerunDev]

Thanks a lot for this contribution @Aelysya!
I'll test it next week, to make sure I have the time to do so.
Plus, will be better to add the PSDK part too I think.

[AerunDev]

Testé, fonctionnel, c'est propre, point faible ? Trop fort. 💪