fix: peer-dependencies and target for JS codegen

[phillip-cashen]

Hello DA Daml team!

i have a small PR here that i hope you would take a look that addresses two minor concerns/problems i saw when using the codegen.

this PR fixes two areas in the javascript/typescript code generation.

1. its called "peerDependencies" and not "peer-dependencies" (https://docs.npmjs.com/cli/v7/configuring-npm/package-json#peerdependencies)
2. "es5" has end-of-life with typescript 6.0, so updating to es2015 makes sense, epseically since it is already included in the "lib" section anyway.