Simple Browser Extension to Embed Source Links in JDK Docs

[cretz]

• E.g. https://docs.oracle.com/javase/8/docs/api/java/time/ZoneId.html#of-java.lang.String- would have a link to https://github.com/dmlloyd/openjdk/blob/ead4a054c3b4d9caa3f46636de37f71d9c3a5773/jdk/src/java.base/share/classes/java/time/ZoneId.java#L294 like the Scala docs do
• Maybe integrate with sourcegraph
• Good way to learn about browser extension dev since this is such a simple task and probably a good way to test FF's WebExtension support compat w/ Chrome