[install-guide] Start translation

Create an empty RST file, our scripts will add content to it.
Enable translation via the config file.

Change-Id: I30999b468c1155e423d70fb7cd7d6161ac97aab9
Implements: blueprint installguide-liberty

doc-tools-check-languages.conf

@@ -36,9 +36,10 @@ declare -A SPECIAL_BOOKS=(
     ["user-guide"]="RST"
     ["user-guide-admin"]="RST"
     ["networking-guide"]="RST"
+    # In process of migration to RST
     ["admin-guide-cloud-rst"]="RST"
-    # Skip guide while it's moved to RST.
-    ["install-guide-rst"]="skip"
+    ["install-guide-rst"]="RST"
+    # Skip guide while it's created
     ["contributor-guide"]="skip"
     # This needs special handling, handle it with the RST tools.
     ["common-rst"]="RST"