Include tutorial in modeling guide (#206)

* external events API example

* Include tutorial in mission modeling guide PDF

generate-pdfs/aerie-mission-modeling-guide.txt

@@ -9,3 +9,18 @@ https://nasa-ammos.github.io/aerie-docs/mission-modeling/parameters/
 https://nasa-ammos.github.io/aerie-docs/mission-modeling/activity-mappers/
 https://nasa-ammos.github.io/aerie-docs/mission-modeling/value-schemas/
 https://nasa-ammos.github.io/aerie-docs/mission-modeling/advanced-the-merlin-interface/
+https://nasa-ammos.github.io/aerie-docs/tutorials/mission-modeling/introduction/
+https://nasa-ammos.github.io/aerie-docs/tutorials/mission-modeling/first-build/
+https://nasa-ammos.github.io/aerie-docs/tutorials/mission-modeling/first-resource/
+https://nasa-ammos.github.io/aerie-docs/tutorials/mission-modeling/first-activity/
+https://nasa-ammos.github.io/aerie-docs/tutorials/mission-modeling/first-model-test/
+https://nasa-ammos.github.io/aerie-docs/tutorials/mission-modeling/enum-derived-resource/
+https://nasa-ammos.github.io/aerie-docs/tutorials/mission-modeling/current-value/
+https://nasa-ammos.github.io/aerie-docs/tutorials/mission-modeling/second-look/
+https://nasa-ammos.github.io/aerie-docs/tutorials/mission-modeling/integrating-rate/
+https://nasa-ammos.github.io/aerie-docs/tutorials/mission-modeling/integration-comparison/
+https://nasa-ammos.github.io/aerie-docs/tutorials/mission-modeling/simulation-config/
+https://nasa-ammos.github.io/aerie-docs/tutorials/external-events/introduction/
+https://nasa-ammos.github.io/aerie-docs/tutorials/external-events/creating-an-external-source/
+https://nasa-ammos.github.io/aerie-docs/tutorials/external-events/uploading-an-external-source/
+https://nasa-ammos.github.io/aerie-docs/tutorials/external-events/associating-derivation-groups/