pass Client-SDK HTTP header

This will only work when pointed to the next version of the SDK.

J=SLAP-1949
TEST=manual,auto

see that the test-site specifies the theme's version in the header
create a fresh jambo site using the hitchhiker theme, see the header passed as expected

hooks/templatedataformatter.js

@@ -1,4 +1,5 @@
 const getCleanedJamboInjectedData = require('../static/webpack/getCleanedJamboInjectedData');
+const packageJson = require('../package.json');
 
 /**
  * Formats the data sent to the handlebars templates during Jambo builds.
@@ -25,7 +26,8 @@ module.exports = function (pageMetadata, siteLevelAttributes, pageNameToConfig)
     params: currentLocaleConfig.params || {},
     relativePath,
     env: {
-      JAMBO_INJECTED_DATA: env.JAMBO_INJECTED_DATA
+      JAMBO_INJECTED_DATA: env.JAMBO_INJECTED_DATA,
+      packageJsonVersion: packageJson.version
     }
   };
   if (globalConfig.useJWT) {

script/core.hbs

@@ -18,6 +18,9 @@
       {{#with env.JAMBO_INJECTED_DATA}}
         {{#if businessId}}businessId: "{{businessId}}",{{/if}}
       {{/with}}
+      customClientSdk: {
+        ANSWERS_THEME: '{{{ env.packageJsonVersion }}}'
+      }
     };
     const userConfig = {
       {{#with (deepMerge global_config (lookup verticalsToConfig verticalKey) pageSettings) }}