fix: resolve relative image paths in step.html viewer

Images referenced from markdown files with relative paths (e.g., ./images/foo.png)
were broken when rendered through step.html on GitHub Pages. Added path rewriting
in loadStep() to resolve image URLs against the markdown file's directory.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: brunoborges

docs/step.html

@@ -375,6 +375,13 @@
                 let md = await response.text();
                 md = processMarkdown(md);
 
+                // Fix relative image paths to resolve against the markdown file's directory
+                const stepDir = step.file.substring(0, step.file.lastIndexOf('/') + 1);
+                md = md.replace(/!\[([^\]]*)\]\((?!https?:\/\/|\/\/)([^)]+)\)/g, (match, alt, path) => {
+                    const cleanPath = path.replace(/^\.\//, '');
+                    return `![${alt}](${GITHUB_RAW_BASE}${stepDir}${cleanPath})`;
+                });
+
                 marked.setOptions({ breaks: true, gfm: true });
                 document.getElementById('markdown-content').innerHTML = marked.parse(md);