Add README.md and remove others

Author: tatsuhiro-t

README

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+# sfparse-rs
+
+sfparse-rs is [RFC
+9651](https://datatracker.ietf.org/doc/html/rfc9651) Structured Field
+Values parser written in Rust.  It is the port of
+[sfparse](https://github.com/ngtcp2/sfparse) written in C.
+
+It is designed not to do any extra allocation, like allocating maps,
+lists, and Strings, and do the minimal stuff to parse the input data.
+
+```rust
+use sfparse::{Parser, Value};
+
+let mut urgency :i32 = 3;
+let mut incremental = false;
+let mut p = Parser::new("u=2, i".as_bytes());
+
+loop {
+    match p.parse_dict().unwrap() {
+        None => break,
+        Some(("u", Value::Integer(v))) if (0i64..=7i64).contains(&v) => urgency = v as i32,
+        Some(("i", Value::Bool(v))) => incremental = v,
+        _ => (),
+    }
+}
+
+println!("urgency={urgency} incremental={incremental}");
+```
+
+## License
+
+The MIT License
+
+Copyright (c) 2024 sfparse-rs contributors