feat: add Midas EBNF

syntax/midas.ebnf

@@ -0,0 +1,26 @@
+identifier ::= '[a-zA-Z][a-zA-Z_]*'
+
+integer ::= '\d+'
+number ::= integer ["." integer]
+boolean ::= "False" | "True"
+none ::= "None"
+
+value ::= number | boolean | none
+lambda-value ::= "_" | value
+lambda-operator ::= ">" | "<" | ">=" | "<=" | "==" | "!="
+lambda ::= lambda-value lambda-operator lambda-value
+
+constraint ::= identifier | "(" lambda ")"
+base-type ::= identifier
+type ::= base-type { "+" constraint }
+
+type-property ::= 'identifier' ":" 'type'
+type-body ::= "{" { 'type-property' } "}"
+
+operation-type ::= "<" 'type' ">"
+
+type-statement ::= "type" 'identifier' "<" 'type' {"," 'type'} ">" ['type-body']
+operation-statement ::= "op" 'operation-type' 'operator' 'operation-type' "=" 'operation-type'
+constraint-statement ::= "constraint" 'identifier' "=" 'lambda'
+
+statement ::= type-statement | operation-statement | constraint-statement