chore: simplify copy commands

functions/Dockerfile.emulator

@@ -6,15 +6,17 @@
 #
 # Optionally, initial data can be setup by mounting `/app/seed`.
 #
-# COMMANDS (used from the root directory of the project):
+# COMMANDS
+# We need some files from the root directory of the project,
+# therefore these commands should be ran from the root directory.
 #
 #   BUILD
 #   docker build -f ./functions/Dockerfile.emulator -t emulator .
 #
 #   RUN
 #   docker run -v ./functions:/app/functions -p 4001-4008:4001-4008 -it emulator
 #
-#   EXPORT
+#   EXPORT FIREBASE DATA (while the container is running)
 #   docker exec -it <conatiner_name> /app/export.sh
 #
 # HOW TO DEBUG THE CONTAINER WHILE IT IS RUNNING:
@@ -24,6 +26,15 @@
 #   4) Run `docker exec -it <conatiner_name> bash` command.
 #
 # TECHNICAL NOTES:
+#   WHAT IS THAT DOT AT THE END OF THE BUILD COMMAND?
+#   That is the `context` argument. For the COPY command,
+#   the part that happens on the host machine is done
+#   relative to it.
+#
+#   So if you are in the root directory it will start from there.
+#   https://docs.docker.com/build/building/context/#filesystem-contexts
+#
+#   FIREBASE.JSON HOSTS
 #   Due to Docker, the Firebase emulators should run on 0.0.0.0
 #   https://stackoverflow.com/a/52518929
 #
@@ -56,10 +67,10 @@ RUN \
   firebase setup:emulators:storage && \
   firebase setup:emulators:pubsub
 
-COPY ./../firebase.json               ./firebase.json
-COPY ./../firebase.storage.rules      ./firebase.storage.rules
-COPY ./../firestore.indexes.json      ./firestore.indexes.json
-COPY ./../firestore.rules             ./firestore.rules
+COPY ./firebase.json               ./firebase.json
+COPY ./firebase.storage.rules      ./firebase.storage.rules
+COPY ./firestore.indexes.json      ./firestore.indexes.json
+COPY ./firestore.rules             ./firestore.rules
 
 # Create script for easy exporting
 RUN \