DOC-3395: Improve quickstart keywords for selector/ID discoverability (#4059)

Add selector, textarea, id, tinymce.init keywords to all quickstart
pages (cloud, npm, php, .net, zip) to address Context7 benchmark
Q1 (62/100).

Author: kemister85

modules/ROOT/pages/cloud-quick-start.adoc

@@ -1,8 +1,8 @@
 = Quick start: {productname} from {cloudname}
 :navtitle: Quick start: Cloud
 :description_short: Setup a basic {productname} {productmajorversion} editor using the {cloudname}.
-:description: Get an instance of {productname} {productmajorversion} up and running using the {cloudname}.
-:keywords: tinymce, script, textarea
+:description: Get an instance of {productname} {productmajorversion} up and running using the {cloudname}. Initialize the editor on a textarea element using its ID with tinymce.init and the selector option.
+:keywords: tinymce, script, textarea, selector, id, #mytextarea, tinymce.init, initialize, quick start
 :productSource: cloud
 
 

modules/ROOT/pages/dotnet-projects.adoc

@@ -1,7 +1,7 @@
 = Installing {productname} for .NET
 :navtitle: .NET projects
 :description: Learn how to install {productname} from NuGet.
-:keywords: nuget .net install
+:keywords: nuget, .net, install, selector, textarea, id, tinymce.init
 
 == Install {productname} using NuGet
 

modules/ROOT/pages/npm-projects.adoc

@@ -1,7 +1,7 @@
 = Quick start: {productname} from NPM or Yarn
 :navtitle: Quick start: NPM/Yarn
 :description: Learn how to install {productname} from NPM using NPM and Yarn, including premium plugins for commercial customers.
-:keywords: yarn, npm, javascript, install, premium plugins, tinymce-premium
+:keywords: yarn, npm, javascript, install, premium plugins, tinymce-premium, selector, textarea, id, tinymce.init
 
 == Install {productname} using NPM or Yarn
 

modules/ROOT/pages/php-projects.adoc

@@ -1,7 +1,7 @@
 = Installing {productname} with Composer
 :navtitle: PHP projects
 :description: Learn how to install {productname} from Packagist using Composer.
-:keywords: php, composer, packagist, install
+:keywords: php, composer, packagist, install, selector, textarea, id, tinymce.init
 
 == Install {productname} using the Composer package manager
 

modules/ROOT/pages/zip-install.adoc

@@ -1,7 +1,7 @@
 = Quick start: {productname} from .zip
 :navtitle: Quick start: ZIP
 :description: Learn how to use {productname} from a .zip archive.
-:keywords: zip, archive, unzip, install
+:keywords: zip, archive, unzip, install, selector, textarea, id, tinymce.init
 
 == Install {productname} using a .zip package