feat(rendering): gate rendering based on valid version identifiers (#4614)

* create VersionPragmaFilter component

* use VersionPragmaFilter in BaseLayout

* tighten version idenitifier constraints

* handle case where user specifies a valid `swagger` and `openapi` field

* add traceable class names for each message

* add tests

* linter fixes!

* UNRELATED CHANGE: remove travis short-circuit

* add bypass switch to VersionPragmaFilter

src/style/_layout.scss

@@ -796,3 +796,30 @@ a.nostyle {
     cursor: pointer;
   }
 }
+
+.version-pragma {
+  height: 100%;
+  padding: 5em 0px;
+
+  &__message {
+    display: flex;
+    justify-content: center;
+    height: 100%;
+    font-size: 1.2em;
+    text-align: center;
+    line-height: 1.5em;
+
+    padding: 0px .6em;
+
+    > div {
+      max-width: 55ch;
+      flex: 1;
+    }
+
+    code {
+      background-color: #dedede;
+      padding: 4px 4px 2px;
+      white-space: pre;
+    }
+  }
+}