Update requirements for doc building

Added requirements-docs.txt file
It now loads all centralized upper contraints from ONAP doc

Issue-ID: CPS-704
Signed-off-by: lukegleeson <luke.gleeson@est.tech>
Change-Id: Iee2db84f5b9b7a320cfdbcc11b7b8079971a64a4
diff --git a/docs/requirements-docs.txt b/docs/requirements-docs.txt
new file mode 100644
index 0000000..5a3d2f1
--- /dev/null
+++ b/docs/requirements-docs.txt
@@ -0,0 +1 @@
+lfdocs-conf
\ No newline at end of file
diff --git a/docs/tox.ini b/docs/tox.ini
index 78293e2..0f25a72 100644
--- a/docs/tox.ini
+++ b/docs/tox.ini
@@ -24,6 +24,8 @@
 [testenv:docs]
 basepython = python3
 deps = -r{toxinidir}/requirements-docs.txt
+       -chttps://git.onap.org/doc/plain/etc/upper-constraints.os.txt
+       -chttps://git.onap.org/doc/plain/etc/upper-constraints.onap.txt
 commands =
     sphinx-build -b html -n -d {envtmpdir}/doctrees ./ {toxinidir}/_build/html
     echo "Generated docs available in {toxinidir}/_build/html"
@@ -34,6 +36,9 @@
 
 [testenv:docs-linkcheck]
 basepython = python3
+deps = -r{toxinidir}/requirements-docs.txt
+       -chttps://git.onap.org/doc/plain/etc/upper-constraints.os.txt
+       -chttps://git.onap.org/doc/plain/etc/upper-constraints.onap.txt
 commands = echo "Link Checking not enforced"
 whitelist_externals =
     echo