👌 IMPROVE: External links in new tab (#856)

Add support to enable external links to open in a new tab. Expose the
configuration option myst_links_external_new_tab, which if set will set
all URL links to open in a new tab on the browser.

Besides that, we allow the user to set the target and rel attributes
when using the extension inline_attrs (#820).

Closes #820
Closes #856

Signed-off-by: Marjus Cako <marios.cako@hpe.com>

myst_parser/config/main.py

@@ -233,6 +233,14 @@ def __repr__(self) -> str:
         },
     )
 
+    links_external_new_tab: bool = dc.field(
+        default=False,
+        metadata={
+            "validator": instance_of(bool),
+            "help": "Open all external links in a new tab",
+        },
+    )
+
     url_schemes: Dict[str, Optional[UrlSchemeType]] = dc.field(
         default_factory=lambda: {
             "http": None,

myst_parser/mdit_to_docutils/base.py

@@ -952,8 +952,12 @@ def render_link_url(
         """
         ref_node = nodes.reference()
         self.add_line_and_source_path(ref_node, token)
+        attribute_keys = ["class", "id", "reftitle", "target", "rel"]
+        if self.md_config.links_external_new_tab:
+            token.attrs["target"] = "_blank"
+            token.attrs["rel"] = "noreferer noopener"
         self.copy_attributes(
-            token, ref_node, ("class", "id", "reftitle"), aliases={"title": "reftitle"}
+            token, ref_node, attribute_keys, aliases={"title": "reftitle"}
         )
         uri = cast(str, token.attrGet("href") or "")
         implicit_text: str | None = None