replace def = value with def: value, and let a = b with a = b

in the name of terseness

i'm also slipping in a new brush preset that i made

closes #125

crates/haku/src/lexer.rs

@@ -73,7 +73,6 @@ fn ident(l: &mut Lexer<'_>) -> TokenKind {
         "or" => TokenKind::Or,
         "if" => TokenKind::If,
         "else" => TokenKind::Else,
-        "let" => TokenKind::Let,
         _ => TokenKind::Ident,
     }
 }
@@ -210,6 +209,7 @@ fn token(l: &mut Lexer<'_>) -> (TokenKind, Span) {
         '[' => one(l, TokenKind::LBrack),
         ']' => one(l, TokenKind::RBrack),
         ',' => one(l, TokenKind::Comma),
+        ':' => one(l, TokenKind::Colon),
         '\\' => one(l, TokenKind::Backslash),
 
         _ => {