expose the bank vault to the script engine

[Helianthella]

Pull Request Prelude

• I have followed proper Hercules code styling.
• I have read and understood the contribution guidelines before making this PR.
• I am aware that this PR will be closed if the above-mentioned criteria are not fulfilled.

Changes Proposed

• Expose map_session_data->status.bank_vault as BankVault to the script engine
• Expose MAX_BANK_ZENY to the script engine
• Update the documentation to reflect those changes

Why expose the vault?

• Allows NPCs to manipulate the vault, so players with a client that does not support the vault packets can still deposit and withdraw money through a NPC.

Example

if (Zeny >= .@val && (BankVault + .@val) <= MAX_BANK_ZENY) {
    Zeny -= .@val;
    BankVault += .@val;
}

Affected Branches: master
Type: enhancement
Compopents: core, script engine, documentation
Tested on: ManaPlus
Needs testing on the official client

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_{linked to https://gitlab.com/evol/serverdata/merge_requests/106}

[HerculesWSAPI]

This change is 

[4144]

not sure is possible add any custom contants here. I think they related to aegis or client constants?

[dastgirp]

The first 100 are used by client, all constant above 100 are not related to client/aegis.

[Helianthella]

@MishimaHaruna @4144 is there anything you want me to change?

[MishimaHaruna]

Nothing to change, looks good to me.

I'm merging it, thank you!