javadoc tool generates pages with an invalid heading order

When the javadoc tool compiles a java doc, it adds a title with a <h1> header tag. If the source starts with a header lower than h2, such as h3 in the following cases, the resulting page will have an invalid heading order.

While we're fixing these particular cases manually, it would be good if the tool could be improved to recognize the issue and fix it during the compilation process.

3. Heading order invalid
docs/api/java.base/java/time/temporal/package-summary.html <h3>Fields and Units</h3>
docs/api/java.base/java/time/chrono/package-summary.html <h3>Example</h3>
docs/api/java.base/java/time/zone/package-summary.html <h3>Package specification</h3>
docs/api/java.base/java/time/package-summary.html <h3>Dates and Times</h3>
docs/api/java.base/java/time/format/package-summary.html <h3>Package specification</h3>
docs/api/java.base/java/lang/package-summary.html <h3>Character Encodings</h3>
docs/api/java.base/java/nio/file/package-summary.html <h3><a id="links">Symbolic Links</a></h3>