chore(devcontainer): move pre-commit install to postAttach.sh

Moved the `initialize hook environments` and `manage commit-msg hooks` commands
to postAttach.sh similar to the approach used in other cal-itp repos.

.devcontainer/Dockerfile

@@ -12,10 +12,3 @@ RUN pip install -e .[dev,test]
 # docs requirements are in a separate file for the GitHub Action
 COPY docs/requirements.txt docs/requirements.txt
 RUN pip install -r docs/requirements.txt
-
-# install pre-commit environments in throwaway Git repository
-# https://stackoverflow.com/a/68758943
-COPY .pre-commit-config.yaml .
-RUN git init . && \
-    pre-commit install-hooks && \
-    rm -rf .git

.devcontainer/postAttach.sh

@@ -4,4 +4,9 @@ set -eu
 # initialize pre-commit
 
 git config --global --add safe.directory /calitp/app
-pre-commit install --overwrite
+
+# initialize hook environments
+pre-commit install --install-hooks --overwrite
+
+# manage commit-msg hooks
+pre-commit install --hook-type commit-msg