Polish some minor visuals on the splash page. (#452)
Polish some minor visuals on the splash page. (#452)

- Fixes the video mime type to match the video file

- Makes the video `cover` instead of `fill`, which avoids distortion at
  larger sizes.

- Adds a gradient scrim as a replacement for the opacity the video
  previously had, which makes the transition from video -> grey less
  abrupt and feels more intentional.

- Reduces the spacing between paragraphs slightly
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