conlang: Rename literals; split, compose, and document Rules

- Renamed literal Types to reflect their literal nature
  - This allows for consistent naming across future non-literal Types
- Complicated lexer Rules have been split into composable sub-rules,
  and moved into the Rule struct.
  - This improves modularity, and allows sharing of sub-rules across rules.
- Documented each lexer rule with (at least) a one-line blurb
  describing its function

libconlang/examples/identify_tokens.rs

@@ -1,18 +1,16 @@
 //! This example grabs input from stdin, lexes it, and prints which lexer rules matched
 #![allow(unused_imports)]
 use conlang::lexer::Lexer;
-use std::{io::stdin, error::Error};
+use std::{error::Error, io::stdin};
 
-fn main() -> Result<(), Box<dyn Error>>{
+fn main() -> Result<(), Box<dyn Error>> {
     // get input from stdin
     for line in stdin().lines() {
         let line = line?;
-        // lex the line
-        for func in [Lexer::line_comment, Lexer::block_comment, Lexer::shebang_comment, Lexer::identifier, Lexer::integer, Lexer::float, Lexer::string] {
-            if let Some(token) = func(&mut Lexer::new(&line)) {
-                println!("{:?}: {}", token, &line[token.range()])
-            }
+        let mut lexer = Lexer::new(&line);
+        while let Some(token) = lexer.any() {
+            println!("{:?}: {}", token, &line[token.range()])
         }
     }
     Ok(())
-}
+}