Do not prevent deploy if linkcheck fails

Author: satterly

.github/workflows/tests.yml

@@ -24,7 +24,7 @@ jobs:
       - name: linkcheck
         id: linkcheck
         run:
-          sphinx-build -M linkcheck source build
+          sphinx-build -M linkcheck source build || true
       - name: spelling
         id: spelling
         run:

source/conf.py

@@ -53,3 +53,7 @@
 # html_theme = 'piccolo_theme'
 html_static_path = ['_static']
 html_extra_path = []
+
+linkcheck_ignore = [
+    'https://www.sto.nato.int/publications/STO%20Meeting%20Proceedings/STO-MP-SCI-300/MP-SCI-300-10.pdf',
+]