add case0 to syntax since that is possible sometimes

lib/Quox/Parser/Lexer.idr

@@ -185,7 +185,7 @@ reserved =
    Sym "∷" `Or` Sym "::",
    Punc1 '.',
    Word1 "case",
-   Word1 "case1",
+   Word1 "case0", Word1 "case1",
    Word "caseω" `Or` Word "case#",
    Word1 "return",
    Word1 "of",

lib/Quox/Parser/Parser.idr

@@ -165,7 +165,7 @@ lamIntro = symbolsC [(Lam, "λ"), (DLam, "δ")]
 
 private covering
 caseIntro : Grammar True Qty
-caseIntro = symbols [(One, "case1"), (Any, "caseω")]
+caseIntro = symbols [(Zero, "case0"), (One, "case1"), (Any, "caseω")]
         <|> resC "case" *>
               (qty <* resC "." <|>
                fatalError {c = True} "missing quantity on 'case'")