Readthedocs support (#22)

* Update README

* Add readthedocs builder

* Add supported builders to info text

Author: Daltz333

sphinxext/rediraffe.py

@@ -39,6 +39,8 @@
 
 RE_OBJ = re.compile(r"(?:(\"|')(.*?)\1|(\S+))\s+(?:(\"|')(.*?)\4|(\S+))")
 
+READTHEDOCS_BUILDERS = ["readthedocs", "readthedocsdirhtml"]
+
 
 def create_graph(path: Path) -> Dict[str, str]:
     """
@@ -134,9 +136,12 @@ def build_redirects(app: Sphinx, exception: Union[Exception, None]) -> None:
         logger.info("rediraffe: Redirect generation skipped for linkcheck builders.")
         return
 
-    if type(app.builder) not in (StandaloneHTMLBuilder, DirectoryHTMLBuilder):
+    if (
+        type(app.builder) not in (StandaloneHTMLBuilder, DirectoryHTMLBuilder)
+        and app.builder.name not in READTHEDOCS_BUILDERS
+    ):
         logger.info(
-            "rediraffe: Redirect generation skipped for unsupported builders. Supported builders: html, dirhtml"
+            "rediraffe: Redirect generation skipped for unsupported builders. Supported builders: html, dirhtml, readthedocs, readthedocsdirhtml."
         )
         return