add JOSS GH workflow to build paper PDF

- fix #3
- source: https://github.com/Becksteinlab/zarrtraj/blob/main/.github/workflows/draft-pdf.yml

Author: orbeckst

.github/workflows/draft-pdf.yml

@@ -0,0 +1,25 @@
+on:
+  push:
+    paths:
+      - *.md
+      - *.bib
+      - figures/**
+      - .github/workflows/draft-pdf.yml
+
+jobs:
+  paper:
+    runs-on: ubuntu-latest
+    name: Paper Draft
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Build draft PDF
+        uses: openjournals/openjournals-draft-action@master
+        with:
+          journal: joss
+          paper-path: paper.md
+      - name: Upload
+        uses: actions/upload-artifact@v4
+        with:
+          name: paper
+          path: paper.pdf