Undo monorepo conversion

[javagl]

This is essentially one big "CTRL+Z" for the things that have been done in #64 . The goal is to eventually have a single 3d-tiles-tools package, because there have been some open questions about establishing an organization called 3d-tiles-tools on NPM for publishing the scoped @3d-tiles-tools/... packages.

For now, the contents of the workspaces/packages are moved back into a "flat" src folder. The build infrastructure (i.e. the individual tsconfig.json and package.json files) is removed. Further details will be added here soon.

[javagl]

The conversion back to a "not-monorepo" is done.

The original workspaces/packages have been moved back into the top-level /src folder.

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Some details:

The directory structure within this folder might look a bit unusual at the first glance: There are files like
src/base/base/Buffers.ts or
src/ktx/ktx/KtxUtility.ts
The reason for that is that the first subdirectory corresponds to the "package name", and the second subdirectory level reflects the structure within that package. Each of the first subdirectory levels contains an index.ts file, like
src/base/index.ts
that exports the "API". One reasoning behind that is that cross-package imports can be written in the form
import { BinaryBufferStructure } from "../../base";
which at least more closely resembles the
import { BinaryBufferStructure } from "@3d-tiles-tools/base";
from the packaged version. The alternative would be to descend into the respective subdirectory within the "package", as in
`import { BinaryBufferStructure } from "../../base/binary/BinaryBufferStructure";
Whether or not this really makes sense or is a good practice? I'm open for comments here...

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I tested running the npm install and npm run package scripts (multiple times...).
I've tried out using the resulting package as...

• a basis for installing an running the tools as a command line application
• a dependency in a CommonJS JavaScript project
• a dependency in a ESM JavaScript project
• a dependency in a CommonJS TypeScript project
• a dependency in a ESM TypeScript project
• a dependency for the 3d-tiles-validator.... which actually required zero code changes.

I also ran all demos, and did a short review/cleanup pass of the README and IMPLEMENTATION, and have been ballsy enough to already put a release date into the CHANGES.md. Let's see how this goes...