Set file_scope option

Fixes #886

.github/workflows/build_book.yaml

@@ -59,11 +59,16 @@ jobs:
         uses: actions/cache@v2
         with:
           path: _bookdown_files
-          key: bookdown-1-${{ hashFiles('**/*Rmd') }}
-          restore-keys: bookdown-1-
+          key: bookdown-2-${{ hashFiles('**/*Rmd') }}
+          restore-keys: bookdown-2-
 
       - name: Build site
-        run: Rscript -e 'bookdown::render_book("index.Rmd", quiet = TRUE)'
+        run: |
+          # Allows [implcit heading links] to work; will need to convert
+          # to explicit before switching to visual editor
+          options(bookdown.render.file_scope = FALSE)
+          bookdown::render_book("index.Rmd", quiet = TRUE)
+        shell: Rscript {0}
 
       - name: Deploy to Netlify
         if: contains(env.isExtPR, 'false')