parser: Fix missing check for upper exponent (#665)

parser.go

@@ -968,7 +968,7 @@ byteLoop:
 func (p *parser) scanIntOrFloat(b []byte) (ast.Reference, []byte, error) {
 	i := 0
 
-	if len(b) > 2 && b[0] == '0' && b[1] != '.' && b[1] != 'e' {
+	if len(b) > 2 && b[0] == '0' && b[1] != '.' && b[1] != 'e' && b[1] != 'E' {
 		var isValidRune validRuneFn
 
 		switch b[1] {

unmarshaler_test.go

@@ -155,6 +155,11 @@ func TestUnmarshal_Floats(t *testing.T) {
 			input:    `0e0`,
 			expected: 0.0,
 		},
+		{
+			desc:     "float upper exponent zero",
+			input:    `0E0`,
+			expected: 0.0,
+		},
 		{
 			desc:     "float fractional with exponent",
 			input:    `6.626e-34`,