Start work on lambda functions (WIP)

src/lexer/lexer.c

@@ -11,6 +11,7 @@ struct _SolsTokenTypeMap SolsTokenTypeMap[] = {
     {"if", STT_KW_IF},
     {"while", STT_KW_WHILE},
     {"def", STT_KW_DEF},
+    {"lambda", STT_KW_LAMBDA},
     {"struct", STT_KW_STRUCT},
     {"{", STT_OPEN_CURLY},
     {"}", STT_CLOSE_CURLY},