Docs: Enable RTD on tf-m-tests

Added files required for the tf-m-tests documentation to be displayed on Read the Docs

Change-Id: I073fb19e106eb1c218ebc9fda43cec0aa20c39cf
Signed-off-by: Elena Uziunaite <elena.uziunaite@arm.com>
diff --git a/docs/requirements.txt b/docs/requirements.txt
new file mode 100644
index 0000000..4678dc5
--- /dev/null
+++ b/docs/requirements.txt
@@ -0,0 +1,10 @@
+graphviz
+Jinja2>=3.0.2
+latex
+Sphinx==4.2.0
+m2r2
+sphinx-rtd-theme>=1.0.0
+sphinxcontrib-plantuml==0.22
+sphinxcontrib-svg2pdfconverter==1.1.1
+sphinx-tabs==3.2.0
+docutils==0.16