PLT-6659 Fixed upload thumbnails that weren't properly rotated (#6816)

- Used client-side EXIF data to rotate profile picture thumbnails
- Added a small package for correctly translating EXIF orientation into CSS transforms
- Instead of displaying the image using FileReader, used URL.createObjectURL because it is faster
- For upload thumbnails, the original behavior was scaling the entire original image, without accounting for EXIF rotate. I changed this to use the thumbnail image, which does respect rotation.
- The preview image was not available when the upload request returned, because handling the preview image creation was in a goroutine. I used sync.WaitGroup to block until the preview image creation is done.

webapp/yarn.lock

@@ -2720,6 +2720,10 @@ executable@^1.0.0:
   dependencies:
     meow "^3.1.0"
 
+exif2css@^1.2.0:
+  version "1.2.0"
+  resolved "https://registry.yarnpkg.com/exif2css/-/exif2css-1.2.0.tgz#8438e116921508e3dcc30cbe2407b1d5535e1b45"
+
 exit-hook@^1.0.0:
   version "1.1.1"
   resolved "https://registry.yarnpkg.com/exit-hook/-/exit-hook-1.1.1.tgz#f05ca233b48c05d54fff07765df8507e95c02ff8"