Merge pull request #1829 from zacharyburnett/changelog/fix_rtd_build

fix readthedocs build to not require user input for `towncrier build`

.readthedocs.yaml

@@ -14,7 +14,7 @@ build:
     pre_install:
       - git update-index --assume-unchanged docs/rtd_environment.yaml docs/conf.py
     post_install:
-      - towncrier build
+      - towncrier build --keep
 
 conda:
   environment: docs/rtd_environment.yaml