add sema's logo (#1387)

Will replace with an svg version later when we have it. For now, we can
just get Sema listed with the bitmap logo.

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Nikoś <[email protected]>

Author: 3 people

src/content/sponsors/sema/index.md

@@ -0,0 +1,19 @@
+---
+name: Sema
+url: https://www.semasoftware.com/
+location: "USA"
+description:
+  "Sema is a software company that is squarely focused on understanding and
+  improving tech. We build tools that bring technologists and non-technologists
+  together. Because when that happens, engineers do their best work,
+  organizations build great products, and true innovation can take shape."
+socials:
+  linkedin:
+  twitter:
+  github:
+  discord:
+  mastodon:
+  bluesky:
+tier: Bronze
+logo_padding: 20px 0
+---