resolc crate (#328)

- Factor the YUL crate out of `revive-solidity`.
- `revive-solidity` is in reality not a Solidity implementation but the
revive solidity compiler driver (`resolc`). By renaming we not only get
this straight but also a binary with the same name as the crate which
should be less confusing.

---------

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

crates/yul/src/error.rs

@@ -0,0 +1,15 @@
+//! The Yul IR error.
+
+use crate::lexer::error::Error as LexerError;
+use crate::parser::error::Error as ParserError;
+
+/// The Yul IR error.
+#[derive(Debug, thiserror::Error, PartialEq, Eq)]
+pub enum Error {
+    /// The lexer error.
+    #[error("Lexical error: {0}")]
+    Lexer(#[from] LexerError),
+    /// The parser error.
+    #[error("Syntax error: {0}")]
+    Parser(#[from] ParserError),
+}