This PR adds extra timings for a hot reload.
As an example, before a user might see

> Performing hot reload...                                                
> Reloaded 1 of 788 libraries in 554ms.

With this PR it would instead be something like

> Performing hot reload...                                                
> Reloaded 1 of 788 libraries in 554ms (compile: 33 ms, reload: 153 ms, reassemble: 310 ms).

* Updated file to include version for dependencies.

* Updated clang version to use github revision.

This reverts commit 4ec4c249.

* Update README to respect GitHub site theme

GitHub recently added support for specifying an alternate appearance when the site is using a dark theme [(see the changelog)](https://github.blog/changelog/2022-05-19-specify-theme-context-for-images-in-markdown-beta/). I've implemented this here with download links from https://flutter.dev/brand.

* Change alt text

This reverts commit 180566f2.