Preserve window.location.hash when running a single suite/test using the (‣) buttons

If you're using `window.location.hash` to modify the behavior of your test runner, clicking the (‣) buttons to run a single suite/test will not pass the current hash along.

In my case, I set the value `window.location.hash` to the variation of the source code I wanted to test, then loaded the source files dynamically. This worked fine, but clicking (‣) would not pass `window.location.hash`, which resulted in my loader code not loading any source files.

**Note:** If a test expects `window.location.hash` to be unset when it runs, this could produce unexpected behavior. However, this is already a problem if a test that precedes it sets `window.location.hash`, so I'm very concerned.