Use a `.cspell.json` repo config file

[josecelano]

Add a .cspell.json file in the root dir:

{
  "version": "0.2",
  "language": "en",
  "ignorePaths": [
    ".vscode",
    "**/.git/**",
    "**/vscode-extension/**",
    "megalinter"
  ],
  "words": [
  ]
}

Same as we did for the tracker here: torrust/torrust-tracker#111