Explore reducing package size

**Is your feature request related to a problem? Please describe.**

An npm install of @graphql-codegen/typescript is currently 39MB and includes pretty much the kitchen sink (including babel and core-js)

This is almost solely due to:

1. @graphql-codegen/typescript (39MB) which needs:
2. @graphql-codegen/visitor-plugin-common (39MB) which needs:
3. @graphql-tools/relay-operation-optimizer (36MB) which needs:
4. relay-compiler (33MB) which needs a whole bunch of stuff (103 packages at least)

Given that relay is a very niche need for most graphql typescript users, it seems unfortunate that its inclusion results in the bulk of the package size

**Describe the solution you'd like**

Remove relay-compiler and/or relay-operation-optimizer from the default install and make it optional

**Additional context**

39MB may not sound like too much, but in a project with dozens of deps, it stands out as one of the biggest offenders for a considerably small utility. It also increases the surface area for security issues and (annoying) package update notifications.