message: Fix Ignore anything before begin document in structure
diff: @@ -86,10 +86,10 @@ export class SectionNodeProvider implements vscode.TreeDataProvider<Section> {
  return children
  }
  content = utils.stripCommentsAndVerbatim(content)
  + const startPos = content.search(/\\begin{document}/gm)
  const endPos = content.search(/\\end{document}/gm)
  - if (endPos > -1) {
  - content = content.substring(0, endPos)
  - }
  + const offset = '\\begin{document}'.length
  + content = content.substring(startPos > -1 ? startPos + offset : 0, endPos > -1 ? endPos : undefined)
  const structureModel = new StructureModel(this.extension, filePath, rootStack, children, newFileStack, sectionNumber)
  