docs: prefixes in h1 titles to disambiguate pages

docs/latest/viewer/configuration.md

@@ -1 +1,3 @@
-# Configuration
+# Viewer: Configuration
+
+...

docs/latest/viewer/internationalization.md

@@ -1,4 +1,4 @@
-# Internationalization
+# Viewer: Internationalization
 
 OHIF supports internationalization using [i18next](https://www.i18next.com/)
 through the npm package [@ohif/i18n](https://www.npmjs.com/package/@ohif/i18n),

docs/latest/viewer/themeing.md

@@ -1,4 +1,4 @@
-# Themeing
+# Viewer: Themeing
 
 Themeing is currently accomplished with color variables that are defined within
 the [`:root`](https://css-tricks.com/almanac/selectors/r/root/) selector