Improve landing page and Readme (#50)

## What Changed?

Completes the "repository structure" section and links separately to the
documentation for the flow analyzer and the policy framework.

## Why Does It Need To?

Makes it easier for people to get started. Updates the links to match
the actual new repo structure.

## Checklist

- [x] Above description has been filled out so that upon quash merge we
have a
  good record of what changed.
- [x] New functions, methods, types are documented. Old documentation is
updated
  if necessary
- [x] Documentation in Notion has been updated
- [x] Tests for new behaviors are provided
  - [x] New test suites (if any) ave been added to the CI tests (in
`.github/workflows/rust.yml`) either as compiler test or integration
test.
*Or* justification for their omission from CI has been provided in this
PR
    description.

README.md

@@ -6,13 +6,22 @@ See our [Notion pages](https://www.notion.so/justus-adam/Dataflow-973fca6c36ca42
 for details on [getting started](https://www.notion.so/justus-adam/Getting-Started-40541156c25d48f8b6ad79a0e1b09b91)
 
 For your convenience during development the documentation for the code and rustc
-(which we use as a library) are hosted on our [github pages](https://brownsys.github.io/dfpp).
+(which we use as a library) are hosted on our [github pages][docs]
+
+[docs]: https://brownsys.github.io/dfpp
 
 ## Repository Structure
 
 - `crates`: The source code of the various parts and tools that comprise
   Paralegal
   - `paralegal-spdg`: Definition of the Semantic Program Dependence Graph
-  - `paralegal-flow`: Rustc plugin that extracts an SPDG by means of control and data flow analysis
+  - `paralegal-flow`: Rustc plugin that extracts an SPDG by means of control and
+    data flow analysis
   - `paralegal-policy`: Framework for defining policies as graph queries
   - `paralegal-explore`: Query and visualize parts of an SPDG
+- `prop`: Sample policies we wrote for Open Source Rust applications
+  - `websubmit`: Policy for <https://github.com/ms705/websubmit-rs>
+  - `lemmy`: Policy for <https://github.com/LemmyNet/lemmy>
+- `scripts`: Helper scripts for auxillary tasks. Currently only holds a script
+  for counting lines in Forge files
+- `doc-src`: Sources for building the documentation. that is hosted on [GitHub pages][docs]

doc-src/index.md

@@ -10,5 +10,7 @@ linking against. The compiler docs do not interlink with the docs for the
 how to build them such that they do. As a result the two documentations are
 hosted here separately.
 
-- [Link to the paralegal-flow crate documentation](libs/paralegal_flow/index.html) (dependent, non-rustc crates are linked)
+- Generated rustdocs (dependent, non-rustc crates are linked).
+  - Doc for the [property definition framework](libs/paralegal_policy/index.html)
+  - Internal doc for the [flow analyzer](libs/paralegal_flow/index.html)
 - [Link to the rustc 1.63.0 documentation](compiler/index.html)