docs: add README filter examples for address, pool, and DRep

[wolf31o2]

Goal

Add filter examples to README.md for the cases not currently covered. The existing Filtering section already documents type, asset fingerprint, policy ID, and combinations; address, pool ID, and DRep filters have no examples yet.

Files

• README.md (extend the Filtering section that begins at the existing ## Filtering heading)

Changes

Add subsections under the existing Filtering section:

• Address filtering: bech32 address example, multiple addresses, CLI and YAML config samples.
• Pool ID filtering: pool ID format reminder, single and multiple values, CLI and YAML samples.
• DRep filtering: bech32 and hex DRep ID formats, CLI and YAML samples. Note the CIP-0129 header byte handling (PR fix(filter): strip CIP-0129 header byte when decoding drep bech32 IDs #678).
• Combined filter behavior: clarify that all configured filters must match (AND across filter types) and that values within a single filter use OR semantics. The existing intro says this; reinforce with one combined example using address plus pool plus type.

Each example must be tested by running the command against a node before landing.

Verification

• README renders correctly on GitHub.
• Each command in the new sections runs without error against a working adder setup.

Dependencies

None.