Update docs to be compatible with the documentation site

[cam-schultz]

Context and scope
The docs website (https://docs.avax.network/) converts markdown into a beautified website. In order to do this, we need to make the following changes to https://github.com/ava-labs/teleporter/blob/main/contracts/src/Teleporter/README.md and https://github.com/ava-labs/teleporter/tree/main/contracts/src/CrossChainApplications#getting-started-with-an-example-application

• Put all documentation intended for the site in standalone markdown files (for example, separate the Getting Started section into its own file)
• Convert all relative paths in links to absolute paths
• Close all html tags

[michaelkaplan13]

Closing as completed thanks to the ongoing DevRel effort to keep the docs up to date 🙏