Thread names lost when using `#title=` hash fragment

With multi-threaded profiles, setting `#title=` turns every thread's name into the title, which makes them difficult to tell them apart. When there are multiple threads, I'd prefer if it kept the original thread names from the file, and just change `document.title`.

For example, when I want to look at `MainThread` here: https://www.speedscope.app/#profileURL=https%3A%2F%2Frawcdn.githack.com%2Fgjoseph92%2Fdask-profiling-coiled%2Fe48d1e07ff9ab9f61360e04b597d0b58c0e3e2c8%2Fresults%2Fcython.json%3Fraw%3Dtrue

It's harder to find here: https://www.speedscope.app/#profileURL=https%3A%2F%2Frawcdn.githack.com%2Fgjoseph92%2Fdask-profiling-coiled%2Fe48d1e07ff9ab9f61360e04b597d0b58c0e3e2c8%2Fresults%2Fcython.json%3Fraw%3Dtrue&title=cython

I imagine the change would just happen on this line:
https://github.com/jlfwong/speedscope/blob/b71cef5db4162e9cd871ad7a1bf5716fffabe5ff/src/views/application.tsx#L207
and maybe also https://github.com/jlfwong/speedscope/blob/b71cef5db4162e9cd871ad7a1bf5716fffabe5ff/src/views/application.tsx#L194-L199

If it's that simple, I'm happy to make a PR.