feat(external-links): add whitelist to bypass redirect page (#6548)

Signed-off-by: Tobias Dillig <tobias.dillig@frachtwerk.de>
Signed-off-by: Tobi <tldev-de@users.noreply.github.com>

docs/content/configuration.md

@@ -44,6 +44,7 @@ to work.*
 | `dbURL`              | `CMD_DB_URL`              | **`undefined`**, `postgres://username:password@localhost:5432/hedgedoc`, `mysql://username:password@localhost:3306/hedgedoc`, or `sqlite:///path/to/hedgedoc.db`                      | Set the db in URL style. If set, then the relevant `db` config entries will be overridden.                                                                                                                 |
 | `loglevel`           | `CMD_LOGLEVEL`            | **`info`**, `debug` ...                                                                                                                             | Defines what kind of logs are provided to stdout. Available options: `debug`, `verbose`, `info`, `warn`, `error`                                                                                           |
 | `forbiddenNoteIDs`   | `CMD_FORBIDDEN_NOTE_IDS`  | **`['robots.txt', 'favicon.ico', 'api', 'build', 'css', 'docs', 'fonts', 'js', 'uploads', 'vendor', 'views']`**, `['robots.txt']` or `'robots.txt'` | disallow creation of notes, even if `allowFreeUrl` or `CMD_ALLOW_FREEURL` is `true`                                                                                                                        |
+| `externalLinkWhitelist` | `CMD_EXTERNAL_LINK_WHITELIST` | **`[]`**, `example.com,trusted.org`                                                                                                                 | Comma-separated list of domains (and their subdomains) that bypass the external link warning page. Links to these domains open directly without the `/_link` redirect.                                     |
 | `imageUploadType`    | `CMD_IMAGE_UPLOAD_TYPE`   | **`filesystem`**, `imgur`, `s3`, `minio`, `azure`, `lutim`                                                                                          | Where to upload images. For S3, see our Image Upload Guides for [S3](guides/media/s3-image-upload.md) or [Minio](guides/media/minio-image-upload.md), also there's a whole section on their respective env vars below. |
 | `sourceURL`          | `CMD_SOURCE_URL`          | **no default**, `https://github.com/hedgedoc/hedgedoc/tree/<current commit>`                                                                        | Provides the link to the source code of HedgeDoc on the entry page (Please, make sure you change this when you run a modified version)                                                                     |
 | `tooBusyLag`         | `CMD_TOOBUSY_LAG`         | **`70`**                                                                                                                                            | CPU time for one event loop tick until node throttles connections. (milliseconds)                                                                                                                          |