Describe series/3.x in docs/index.md and regenerate README

Brief intro: a major overhaul of 2.x, highly modular with a
zero-dependency core, high level API built on ZIO Blocks. Also fixes the
install snippet's version — @Version@ falls back to the latest git tag
across the whole repo's history (a 2.x release), which is misleading here;
@SNAPSHOT_VERSION@ resolves to the actual 3.0.0-SNAPSHOT instead.

Author: googley42

README.md

@@ -0,0 +1,52 @@
+[//]: # (This file was autogenerated using `zio-sbt-website` plugin via `sbt generateReadme` command.)
+[//]: # (So please do not edit it manually. Instead, change "docs/index.md" file or sbt setting keys)
+[//]: # (e.g. "readmeDocumentation" and "readmeSupport".)
+
+# ZIO DynamoDB
+
+Simple, type-safe, and efficient access to DynamoDB
+
+[![Experimental](https://img.shields.io/badge/Project%20Stage-Experimental-yellowgreen.svg)](https://github.com/zio/zio/wiki/Project-Stages) ![CI Badge](https://github.com/zio/zio-dynamodb/workflows/CI/badge.svg) [![Sonatype Releases](https://img.shields.io/nexus/r/https/oss.sonatype.org/dev.zio/zio-dynamodb-core_2.13.svg?label=Sonatype%20Release)](https://oss.sonatype.org/content/repositories/releases/dev/zio/zio-dynamodb-core_2.13/) [![Sonatype Snapshots](https://img.shields.io/nexus/s/https/oss.sonatype.org/dev.zio/zio-dynamodb-core_2.13.svg?label=Sonatype%20Snapshot)](https://oss.sonatype.org/content/repositories/snapshots/dev/zio/zio-dynamodb-core_2.13/) [![javadoc](https://javadoc.io/badge2/dev.zio/zio-dynamodb-docs_2.13/javadoc.svg)](https://javadoc.io/doc/dev.zio/zio-dynamodb-docs_2.13) [![ZIO DynamoDB](https://img.shields.io/github/stars/zio/zio-dynamodb?style=social)](https://github.com/zio/zio-dynamodb)
+
+## Introduction
+
+`series/3.x` is a major overhaul of ZIO DynamoDB 2.x: a highly modular library with a
+zero-dependency core, plus a high level API built on [ZIO Blocks](https://zio.dev/zio-blocks).
+It's under active, module-by-module development — modules are being migrated in one at a
+time, so not everything from 2.x is available here yet.
+
+For the current, production-ready release, see the [`series/2.x`
+documentation](https://zio.dev/zio-dynamodb/) instead.
+
+## Installation
+
+To use ZIO DynamoDB 3.x, add the following to your `build.sbt` (not yet published):
+
+```scala
+libraryDependencies ++= Seq(
+  "dev.zio" %% "zio-dynamodb" % "3.0.0-SNAPSHOT"
+)
+```
+
+## Documentation
+
+Learn more on the [ZIO DynamoDB homepage](https://github.com/zio/zio-dynamodb)!
+
+## Contributing
+
+For the general guidelines, see ZIO [contributor's guide](https://zio.dev/contributor-guidelines).
+
+## Code of Conduct
+
+See the [Code of Conduct](https://zio.dev/code-of-conduct)
+
+## Support
+
+Come chat with us on [![Badge-Discord]][Link-Discord].
+
+[Badge-Discord]: https://img.shields.io/discord/629491597070827530?logo=discord "chat on discord"
+[Link-Discord]: https://discord.gg/2ccFBr4 "Discord"
+
+## License
+
+[License](LICENSE)

docs/index.md

@@ -10,10 +10,10 @@ Simple, type-safe, and efficient access to DynamoDB
 
 ## Introduction
 
-This is the `series/3.x` line of ZIO DynamoDB — a from-scratch rewrite built on
-`zio-blocks-schema` rather than `zio-schema`. It is currently at an early, hello-world
-stage: the codebase and this documentation site are both placeholders while the real
-module-by-module import from the rewrite happens.
+`series/3.x` is a major overhaul of ZIO DynamoDB 2.x: a highly modular library with a
+zero-dependency core, plus a high level API built on [ZIO Blocks](https://zio.dev/zio-blocks).
+It's under active, module-by-module development — modules are being migrated in one at a
+time, so not everything from 2.x is available here yet.
 
 For the current, production-ready release, see the [`series/2.x`
 documentation](https://zio.dev/zio-dynamodb/) instead.
@@ -24,6 +24,6 @@ To use ZIO DynamoDB 3.x, add the following to your `build.sbt` (not yet publishe
 
 ```scala
 libraryDependencies ++= Seq(
-  "dev.zio" %% "zio-dynamodb" % "@VERSION@"
+  "dev.zio" %% "zio-dynamodb" % "@SNAPSHOT_VERSION@"
 )
 ```