chore: bump supported tutor versions to work on tutor 18 for redwood

Update the install_requires list to include support for Tutor 18 (and
Open edX Redwood), and update the README.

CHANGELOG.md

@@ -1,3 +1,7 @@
+## Unreleased
+
+* [Enhancement] Support Tutor 18 and Open edX Redwood.
+
 ## Version 1.4.0 (2024-04-05)
 
 * [Enhancement] Support Python 3.12.

README.md

@@ -28,6 +28,7 @@ appropriate one:
 | Olive | `>=15.0, <16` | `main` | 1.1.x |
 | Palm | `>=16.0, <17` | `main` | 1.2.x |
 | Quince | `>=17.0, <18` | `main` | >=1.3.0 |
+| Redwood | `>=18.0, <19` | `main` | >=1.4.0 |
 
 [^1]: For Open edX Maple and Tutor 13, you must run version 13.2.0 or
  later. That is because this plugin uses the Tutor v1 plugin API,

setup.py

@@ -24,7 +24,7 @@
  packages=find_packages(exclude=["tests*"]),
  include_package_data=True,
  python_requires=">=3.8",
- install_requires=["tutor <18, >=14.0.0"],
+ install_requires=["tutor <19, >=14.0.0"],
  setup_requires=["setuptools-scm"],
  entry_points={"tutor.plugin.v1": ["s3 = tutors3.plugin"]},
  classifiers=[