Enable Handlebars syntax highlighting

[ggrossetie]

Here's the code to add from Prism:

!function(h){function v(e,n){return"___"+e.toUpperCase()+n+"___"}Object.defineProperties(h.languages["markup-templating"]={},{buildPlaceholders:{value:function(a,r,e,o){if(a.language===r){var c=a.tokenStack=[];a.code=a.code.replace(e,function(e){if("function"==typeof o&&!o(e))return e;for(var n,t=c.length;-1!==a.code.indexOf(n=v(r,t));)++t;return c[t]=e,n}),a.grammar=h.languages.markup}}},tokenizePlaceholders:{value:function(p,k){if(p.language===k&&p.tokenStack){p.grammar=h.languages[k];var m=0,d=Object.keys(p.tokenStack);!function e(n){for(var t=0;t<n.length&&!(m>=d.length);t++){var a=n[t];if("string"==typeof a||a.content&&"string"==typeof a.content){var r=d[m],o=p.tokenStack[r],c="string"==typeof a?a:a.content,i=v(k,r),u=c.indexOf(i);if(-1<u){++m;var g=c.substring(0,u),l=new h.Token(k,h.tokenize(o,p.grammar),"language-"+k,o),s=c.substring(u+i.length),f=[];g&&f.push.apply(f,e([g])),f.push(l),s&&f.push.apply(f,e([s])),"string"==typeof a?n.splice.apply(n,[t,1].concat(f)):a.content=f}}else a.content&&e(a.content)}return n}(p.tokens)}}}})}(Prism);
!function(e){e.languages.handlebars={comment:/\{\{![\s\S]*?\}\}/,delimiter:{pattern:/^\{\{\{?|\}\}\}?$/i,alias:"punctuation"},string:/(["'])(?:\\.|(?!\1)[^\\\r\n])*\1/,number:/\b0x[\dA-Fa-f]+\b|(?:\b\d+\.?\d*|\B\.\d+)(?:[Ee][+-]?\d+)?/,boolean:/\b(?:true|false)\b/,block:{pattern:/^(\s*~?\s*)[#\/]\S+?(?=\s*~?\s*$|\s)/i,lookbehind:!0,alias:"keyword"},brackets:{pattern:/\[[^\]]+\]/,inside:{punctuation:/\[|\]/,variable:/[\s\S]+/}},punctuation:/[!"#%&':()*+,.\/;<=>@\[\\\]^`{|}~]/,variable:/[^!"#%&'()*+,\/;<=>@\[\\\]^`{|}~\s]+/},e.hooks.add("before-tokenize",function(a){e.languages["markup-templating"].buildPlaceholders(a,"handlebars",/\{\{\{[\s\S]+?\}\}\}|\{\{[\s\S]+?\}\}/g)}),e.hooks.add("after-tokenize",function(a){e.languages["markup-templating"].tokenizePlaceholders(a,"handlebars")})}(Prism);