message: Resolve Add `documentclass` folding
diff: @@ -23,6 +23,7 @@ export class FoldingProvider implements vscode.FoldingRangeProvider {
  private getSectionFoldingRanges(document: vscode.TextDocument) {
  const startingIndices: number[] = this.sectionRegex.map(_ => -1)
  const lines = document.getText().split(/\r?\n/g)
  + let documentClassLine = -1
  const sections: {level: number, from: number, to: number}[] = []
  for (const line of lines) {
  @@ -49,6 +50,16 @@ export class FoldingProvider implements vscode.FoldingRangeProvider {
  ++i
  }
  }
  + if (/\\documentclass/.exec(line)) {
  + documentClassLine = index
  + }
  + if (/\\begin{document}/.exec(line) && documentClassLine > -1) {
  + sections.push({
  + level: 0,
  + from: documentClassLine,
  + to: index - 1
  + })
  + }
  if (/\\end{document}/.exec(line) || index === lines.length - 1) {
  for (let i = 0; i < startingIndices.length; ++i) {
  if (startingIndices[i] === -1) {
  