README: add sponsors section as promised

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

.github/workflows/sponsors.yml

@@ -0,0 +1,36 @@
+name: Generate Sponsors README
+on:
+  push:
+    branches:
+      - main
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Generate Sponsors (bronze) 💖
+        uses: JamesIves/github-sponsors-readme-action@1.0.5
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          file: 'README.md'
+          maximum: 5
+          marker: 'bronze'
+
+      - name: Generate Sponsors (silver) 💖
+        uses: JamesIves/github-sponsors-readme-action@1.0.5
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          file: 'README.md'
+          minimum: 25
+          maximum: 50
+          marker: 'silver'
+
+      - name: Generate Sponsors (gold) 💖
+        uses: JamesIves/github-sponsors-readme-action@1.0.5
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          file: 'README.md'
+          minimum: 100
+          marker: 'gold'

README.md

@@ -63,3 +63,17 @@ There are only two requirements:
 
 1. Pull requests in sub-repositories must have a commit message prefix, e.g. `glfw: <commit message>` to keep our monorepo history nicer - we generally squash merge pull requests so this is not an issue.
 2. Pull requests to this repository may not change multiple sub-repositories in the same commit (e.g. a commit to `glfw/` should not also include changes to `webgpu/`, to avoid confusion.)
+
+## Sponsors
+
+If you like Mach engine, or my other work, you may [sponsor me on GitHub](https://github.com/sponsors/slimsag). This will make my day, it's a huge vote of confidence and I really appreciate your support!
+
+### Silver sponsors ($25/mo)
+
+<!-- silver -->
+<!-- silver -->
+
+### Bronze sponsors ($5/mo)
+
+<!-- bronze -->
+<!-- bronze -->