feat: Azure Cognitive Search Plugin (#815)

* feat(AzureCognitiveSearchPlugin)

* feat(tools/AzureCognitiveSearch.js): Add a new plugin (not structured
  version)
* feat(tools/structured/AzureCognitiveSearch.js): Add a new plugin (structured version)
* feat(tools/manifest.json, tools/index.js, tools/util/handleTools.js):
  Add configurations for the plugin
* feat(api/package.json, package-lock.json): Installed a new package for the
  plugin (@azure/search-documents)
* feat(.env.example): Add new environment variables for the plugin

Here is the link to the corresponding discussion page:
https://github.com/danny-avila/LibreChat/discussions/567

* docs(AzureCognitiveSearchPlugin)

* docs(features/plugins/azure_cognitive_search.md): Add a new document
  for the plugin

* (fix:.env.example)

* reverted extra whitespaces removed by the editor

* docs(mkdocs.yml)

* Add the Azure Cognitive Search Plugin's documentation item to
mkdocs.yml.

api/app/clients/tools/util/handleTools.js

@@ -15,6 +15,8 @@ const {
   OpenAICreateImage,
   StableDiffusionAPI,
   StructuredSD,
+  AzureCognitiveSearch,
+  StructuredACS,
 } = require('../');
 const { loadSpecs } = require('./loadSpecs');
 
@@ -78,6 +80,7 @@ const loadTools = async ({ user, model, functions = null, tools = [], options =
     wolfram: functions ? StructuredWolfram : WolframAlphaAPI,
     'dall-e': OpenAICreateImage,
     'stable-diffusion': functions ? StructuredSD : StableDiffusionAPI,
+    'azure-cognitive-search': functions ? StructuredACS : AzureCognitiveSearch,
   };
 
   const customConstructors = {