chore: add bash script to handle update

my bash is way out of date, but this is a simple script to handle
checking out the desired tag in the submodule, updating the version and
hash in the `__init__.py` file, and then running `gen_proto.sh`.

update.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+
+if [[ -z "$1" ]]; then
+    echo "Usage: bash update.sh version" 1>&2
+    echo ""
+    echo "Example: bash update.sh v0.34.0" 1>&2
+    exit 1
+fi
+
+VERSION=$1
+
+pushd third_party/substrait/
+git checkout $VERSION
+SUBSTRAIT_HASH=$(git rev-parse --short HEAD)
+popd
+
+VERSION=$(echo $VERSION | sed 's/v//')
+
+sed -i "s#__substrait_hash__.*#__substrait_hash__ = \"$SUBSTRAIT_HASH\"#g" src/substrait/__init__.py
+sed -i "s#__substrait_version__.*#__substrait_version__ = \"$VERSION\"#g" src/substrait/__init__.py
+
+./gen_proto.sh