doc: Add documentation-generating scripts to the Crashpad tree

doc/asciidoc.css

+/* Copyright 2015 The Crashpad Authors. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License. */
+
+/* The default AsciiDoc asciidoc.css specifies fuchsia as the visited link
+ * color. This has a dated appearance. Replace it with blue, the same color used
+ * for unvisited links. */
+a:visited {
+  color: blue;
+}