Enable support of ledger device on the portal

[vadaynujra]

Context

With the Polkadot v1.1.0 upgrade, the Pendulum network now supports the generic ledger app, enabling any transaction to be signed using a ledger device. While it was successfully tested using polkadot.js, on the portal the error - This dapp needs to be updated in order to support Ledger signing - was shown

To do

• Identify what the fix is
• Declare the MetadataHash signed extension in the portal (potentially)

[prayagd]

@TorstenStueber @Sharqiewicz estimate ping