Add readthedocs-cli to requirements.in

This will allow us to manage our redirects in-tree.

Signed-off-by: Bence Szépkúti <bence.szepkuti@arm.com>

docs/requirements.in

@@ -1,2 +1,3 @@
-sphinx-rtd-theme
 breathe
+readthedocs-cli
+sphinx-rtd-theme

docs/requirements.txt

@@ -14,6 +14,8 @@ certifi==2022.12.7
     # via requests
 charset-normalizer==3.1.0
     # via requests
+click==8.1.3
+    # via readthedocs-cli
 docutils==0.17.1
     # via
     #   breathe
@@ -27,14 +29,28 @@ importlib-metadata==6.0.0
     # via sphinx
 jinja2==3.1.2
     # via sphinx
+markdown-it-py==2.2.0
+    # via rich
 markupsafe==2.1.2
     # via jinja2
+mdurl==0.1.2
+    # via markdown-it-py
 packaging==23.0
     # via sphinx
 pygments==2.14.0
-    # via sphinx
+    # via
+    #   rich
+    #   sphinx
+pyyaml==6.0
+    # via readthedocs-cli
+readthedocs-cli==4
+    # via -r requirements.in
 requests==2.28.2
-    # via sphinx
+    # via
+    #   readthedocs-cli
+    #   sphinx
+rich==13.3.5
+    # via readthedocs-cli
 snowballstemmer==2.2.0
     # via sphinx
 sphinx==4.5.0