Add feature-hal-spec-spi branch to docs.json

Add SPI feature branch to docs.json, and fix branding of other feature branches.

Author: Amanda Butler

docs.json

@@ -1626,7 +1626,7 @@
         },
         {
             "title": "feature-hal-spec-usb-device doxygen",
-            "description": "The full mbed OS API documentation in doxygen format",
+            "description": "The full Mbed OS API documentation in doxygen format",
             "slug": "feature-hal-spec-usb-device-doxy",
             "hidden": true,
             "type": "doxygen",
@@ -1635,16 +1635,25 @@
         },
         {
             "title": "feature-hal-spec-sai doxygen",
-            "description": "The full mbed OS API documentation in doxygen format",
+            "description": "The full Mbed OS API documentation in doxygen format",
             "slug": "feature-hal-spec-sai-doxy",
             "hidden": true,
             "type": "doxygen",
             "source": "https://github.com/ARMmbed/mbed-os",
             "branch": "feature-hal-spec-sai"
         },
+        {
+            "title": "feature-hal-spec-spi doxygen",
+            "description": "The full Mbed OS API documentation in doxygen format",
+            "slug": "feature-hal-spec-spi-doxy",
+            "hidden": true,
+            "type": "doxygen",
+            "source": "https://github.com/ARMmbed/mbed-os",
+            "branch": "feature-hal-spec-spi"
+        },
         {
             "title": "feature-hal-spec-watchdog doxygen",
-            "description": "The full mbed OS API documentation in doxygen format",
+            "description": "The full Mbed OS API documentation in doxygen format",
             "slug": "feature-hal-spec-watchdog-doxy",
             "hidden": true,
             "type": "doxygen",