Complete installation setup and fix browser sandbox issue

- Add complete installation instructions including ghcup setup
- Create install-deps.sh script for system dependencies
- Fix GHC version compatibility (base >=4.18 instead of 4.21)
- Add puppeteer config to disable sandboxing for mermaid CLI
- Update Mermaid module to use puppeteer config file

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

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

src/Docster/Mermaid.hs

@@ -80,9 +80,10 @@ generateDiagramPaths (DiagramConfig (SourceDir sourceDir) format) (DiagramId dia
 -- | Call mermaid CLI process with appropriate arguments
 callMermaidProcess :: OutputFormat -> FilePath -> FilePath -> IO (Either DocsterError ())
 callMermaidProcess format mmdFile outputFile = do
-  let args = case format of
+  let baseArgs = case format of
         HTML -> ["-i", mmdFile, "-o", outputFile]
         PDF  -> ["-i", mmdFile, "-o", outputFile, "--scale", "3"]
+      args = baseArgs ++ ["--puppeteerConfigFile", "puppeteer-config.json"]
   
   result <- catch
     (callProcess (T.unpack mermaidCommand) args >> return (Right ()))