chore: install standard-version before running bump (aws#11312)

This [PR](aws#11307) migrated our CLI usage of `standard-version` to be used in code as a library. But the library is not installed anywhere.

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bump.sh

@@ -13,4 +13,7 @@
 #
 # --------------------------------------------------------------------------------------------------
 set -euo pipefail
-./scripts/bump.js ${1:-minor}
+scriptdir=$(cd $(dirname $0) && pwd)
+cd ${scriptdir}
+yarn
+${scriptdir}/scripts/bump.js ${1:-minor}

scripts/bump-candidate.sh

@@ -17,4 +17,5 @@
 # --------------------------------------------------------------------------------------------------
 set -euo pipefail
 scriptdir=$(cd $(dirname $0) && pwd)
-BUMP_CANDIDATE=true ${scriptdir}/bump.js ${1:-minor}
+rootdir=${scriptdir}/..
+BUMP_CANDIDATE=true ${rootdir}/bump.sh ${1:-minor}