docs: Add comprehensive Wiki.js version compatibility documentation

Add detailed compatibility documentation and version detection:

- Add Wiki.js 2.x compatibility badge and requirements to README
- Create comprehensive docs/compatibility.md guide
  - Detailed version support matrix (2.2 through 2.5.308+)
  - API schema differences between 2.x and 3.x
  - Version detection examples and troubleshooting
  - Known compatibility issues and solutions
  - Future 3.x support planning
- Enhance test_connection() in both sync and async clients
  - Add API version compatibility detection
  - Better error messages for incompatible versions
  - Detect Wiki.js 3.x and provide clear guidance
- Update package metadata
  - Add Wiki.js compatibility keywords to setup.py and pyproject.toml
  - Add compatibility documentation link to project URLs

SDK supports Wiki.js 2.x (versions 2.2 - 2.5.308+)
Wiki.js 3.x (alpha) not yet supported due to different API schema

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

pyproject.toml

@@ -30,7 +30,7 @@ dependencies = [
     "typing-extensions>=4.0.0",
 ]
 dynamic = ["version"]
-keywords = ["wiki", "wikijs", "api", "sdk", "client", "http", "rest"]
+keywords = ["wiki", "wikijs", "wiki.js", "api", "sdk", "client", "http", "rest", "graphql", "wiki.js-2.x"]
 
 [project.optional-dependencies]
 dev = [
@@ -64,6 +64,8 @@ Homepage = "https://gitea.hotserv.cloud/lmiranda/py-wikijs"
 "Bug Reports" = "https://gitea.hotserv.cloud/lmiranda/py-wikijs/issues"
 Source = "https://gitea.hotserv.cloud/lmiranda/py-wikijs"
 Documentation = "https://gitea.hotserv.cloud/lmiranda/py-wikijs/src/branch/main/docs"
+Compatibility = "https://gitea.hotserv.cloud/lmiranda/py-wikijs/src/branch/main/docs/compatibility.md"
+"Wiki.js" = "https://js.wiki"
 
 [tool.setuptools.dynamic]
 version = {attr = "wikijs.version.__version__"}