New soroban_readme.md for Soroban sdk usage

[sreuland]

What problem does your feature solve?

lack of high level developer focused docs to assist with rapidly writing java sdk code that invokes a soroban contract.

there are many unit tests that demonstrate separate portions of the soroban sdk usage, but a high level opinionated writeup explaining the sdk code that can invoke contracts and navigate the simulations and bump/restore aspects.

What would you like to see?

• a new soroban_readme.md which provides a 'in a nutshell' section on using the sdk to interact with soroban contracts, with a sdk code example of invoking a contract, handling simulation responses, fees, and potential restore/bump retries for expired entries.

• reuse links to existing soroban docs for all high level concepts - https://soroban.stellar.org/docs/category/fundamentals-and-concepts, avoid duplicated content.

• add a section for Development , link to Soroba#RPC for explanation of the stack and how to use quickstart for local dev on standalone or futurenet network.Quickstart#Soroban Development

What alternatives are there?