We use a recent TypeScript version to build maxGraph but applications
that integrates it may be forced to use old TypeScript versions.
We never explain what is the minimum TypeScript version requires to use
`maxGraph`. The changes proposed here are a first step to make this
information available.
It is only informative for now (mentioned in the README) and the minimum
TypeScript version is tested in the `ts-support` package (part of the
'build' GitHub workflow).
Thomas Bouffard