feat: add a simple Crawler example (#453)

While working on Amaru, we'll likely want to grab lots of example data. This adds a small utility to easily grab one block, one tx, or blocks/txs matching some predicate

examples/crawler/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "crawler"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+pallas = { path = "../../pallas" }
+tokio = { version = "1.37", features = ["rt-multi-thread", "macros"] }
+anyhow = "1.0"
+clap = { version = "4.5", features = ["derive", "env"] }
+hex = "0.4.3"