add tron address validation tag with checksum, tests and docs

[imranalperen]

Closes #1519

This PR adds a new trx_addr validation tag for validating TRON mainnet addresses.

TRON addresses use Base58Check encoding, identical to Bitcoin addresses,
with a version byte of 0x41 and a double SHA256 checksum.
The implementation follows the same decoding and checksum verification
approach used by the existing btc_addr validator to ensure consistency.

Included in this PR:

• Base58Check decoding and checksum validation for TRON addresses
• Mainnet version byte validation (0x41)
• Test cases for valid and invalid addresses
• Documentation for the new trx_addr validation tag

[coveralls]

coverage: 73.85% (+0.04%) from 73.814%
when pulling e4d26dd on imranalperen:#1519/feature/trx_addr-tag
into 5010f83 on go-playground:master.

[zemzale]

Implementation seems good.

For others, the spec for it is here: https://github.com/tronprotocol/documentation/blob/master/TRX/Tron-overview.md#61-algorithm-description