setting.jsonに以下を追加

"latex-workshop.latex.recipes": [
  {
    "name": "compile",
    "tools": [
      "latexindent",
      "ptex2pdf",
    ]
  }
],
"latex-workshop.latex.tools": [
  {
    "name": "ptex2pdf",
    "command": "docker",
    "args": [
      "run",
      "--rm",
      "-v",
      "%DIR%:/workdir",
      "paperist/alpine-texlive-ja",
      "ptex2pdf",
      "-l",
      "/workdir/%DOCFILE_EXT%"
    ]
  },{
    "name": "latexindent",
    "command": "docker",
    "args": [
      "run",
      "--rm",
      "-v",
      "%DIR%:/workdir",
      "csegarragonz/latexindent:0.0.1",
      "latexindent",
      "/workdir/%DOCFILE_EXT%",
      "--overwrite"
    ]
  }
],