fix(OAS3): relative urls (#5341)

* Added tooling for appending OAS3 relative URLs to selected Server

Info
* Terms of service URL
* Contact URL
* License URL
* External Docs URL

Tag
* Tag External Docs URL

Operation
* Operation External Docs
** Operation Tag


Co-authored-by: Tim Lai <timothy.lai@gmail.com>

test/mocha/components/info-wrapper.jsx

@@ -17,7 +17,10 @@ describe("<InfoContainer/>", function () {
       url () {},
       basePath () {},
       host () {},
-      externalDocs () {}
+      externalDocs () {},
+    },
+    oas3Selectors: {
+      selectedServer () {},
     },
     getComponent: c => components[c]
   }

test/mocha/components/operations.jsx

@@ -29,6 +29,7 @@ describe("<Operations/>", function(){
       },
       specSelectors: {
         isOAS3() { return false },
+        url() { return "https://petstore.swagger.io/v2/swagger.json" },
         taggedOperations() {
           return fromJS({
           "default": {
@@ -83,6 +84,7 @@ describe("<Operations/>", function(){
       },
       specSelectors: {
         isOAS3() { return true },
+        url() { return "https://petstore.swagger.io/v2/swagger.json" },
         taggedOperations() {
           return fromJS({
           "default": {