tweak pdf generation using custom css

- center images and captions
- prevent images to exceed page width

examples/note_export.py

@@ -44,6 +44,25 @@ def parse_args():
     return parser.parse_args()
 
 
+def create_custom_css_file(path):
+    with open(path, "w") as outfile:
+        outfile.write(
+            """
+img {
+  /* prevent image going out of page */
+  max-width: 100%;
+  /* center image */
+  display: block;
+  margin-left: auto;
+  margin-right: auto;
+}
+figure > figcaption{
+    text-align: center;
+}
+"""
+        )
+
+
 def main():
     args = parse_args()
 
@@ -95,6 +114,7 @@ def main():
                     f"Valid formats: {valid_output_formats}."
                 )
             # special arguments for some output formats
+            create_custom_css_file(Path(tmpdirname) / "custom.css")
             format_kwargs = {
                 # https://github.com/NicklasTegner/pypandoc/issues/186#issuecomment-673282133
                 "pdf": {
@@ -104,6 +124,8 @@ def main():
                         "weasyprint",
                         "--metadata",
                         f"title={candidate.title}",
+                        "--css",
+                        Path(tmpdirname) / "custom.css",
                     ],
                 }
             }