Change placeholder's default font color. Fix some cmps.

DEVSIX-1960

Author: ars18wrw

src/main/resources/com/itextpdf/html2pdf/default.css

@@ -365,6 +365,10 @@ input[type="checkbox"] {
     box-sizing: border-box;
 }
 
+::placeholder {
+    color: darkgray;
+}
+
 select {
     box-sizing: border-box;
     white-space: pre;

src/test/resources/com/itextpdf/html2pdf/css/CssStyleSheetParserTest/cmp_default.css

@@ -474,6 +474,9 @@ input[type="checkbox"] {
     margin: 3px 3px 3px 4px;
     box-sizing: border-box
 }
+::placeholder {
+    color: darkgray
+}
 select {
     box-sizing: border-box;
     white-space: pre;