Prepare to branch for DAP-04

We are starting our DAP-05 implementation (#1669) and so must branch for
DAP-04.

.github/dependabot.yml

@@ -18,3 +18,21 @@ updates:
     schedule:
       interval: "weekly"
     target-branch: "main"
+
+  # Manage dependencies on the release/0.4 branch
+  - package-ecosystem: "cargo"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    target-branch: "release/0.4"
+    open-pull-requests-limit: 20
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    target-branch: "release/0.4"
+  - package-ecosystem: "docker"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    target-branch: "release/0.4"

README.md

@@ -25,7 +25,8 @@ branch.
 | `release/0.1` | [`draft-ietf-ppm-dap-01`](https://datatracker.ietf.org/doc/draft-ietf-ppm-dap/01/) | Yes | Unmaintained as of December 7, 2022 |
 | `release/0.2` | [`draft-ietf-ppm-dap-02`](https://datatracker.ietf.org/doc/draft-ietf-ppm-dap/02/) | Yes | Unmaintained as of July 13, 2023 |
 | `release/0.3` | [`draft-ietf-ppm-dap-03`](https://datatracker.ietf.org/doc/draft-ietf-ppm-dap/03/) | Yes | Unmaintained as of February 6, 2023 |
-| `main` | [`draft-ietf-ppm-dap-04`](https://datatracker.ietf.org/doc/draft-ietf-ppm-dap/04/) | Yes | Supported |
+| `release/0.4` | [`draft-ietf-ppm-dap-04`](https://datatracker.ietf.org/doc/draft-ietf-ppm-dap/04/) | Yes | Supported |
+| `main` | [`draft-ietf-ppm-dap-05`](https://datatracker.ietf.org/doc/draft-ietf-ppm-dap/05/) | [Partial](https://github.com/divviup/janus/issues/1669) | Supported |
 
 ## Building