[DOCS] Adds compatibility matrix to the Install section (#2316)

* [DOCS] Adds compatibility matrix to the Install section and README

Co-authored-by: Fernando Briano <fernando@picandocodigo.net>

README.md

@@ -72,7 +72,16 @@ Please see their respective READMEs for information and documentation.
 
 We follow Ruby’s own maintenance policy and officially support all currently maintained versions per [Ruby Maintenance Branches](https://www.ruby-lang.org/en/downloads/branches/).
 
-Language clients are forward compatible; meaning that clients support communicating with greater or equal minor versions of Elasticsearch. Elasticsearch language clients are only backwards compatible with default distributions and without guarantees made.
+Language clients are forward compatible; meaning that clients support communicating with greater or equal minor versions of Elasticsearch without breaking.
+It does not mean that the client automatically supports new features of newer Elasticsearch versions; it is only possible after a release of a new client version.
+For example, a 8.12 client version won't automatically support the new features of the 8.13 version of Elasticsearch, the 8.13 client version is required for that.
+Elasticsearch language clients are only backwards compatible with default distributions and without guarantees made.
+
+| Gem Version |   | Elasticsearch  Version | Supported |
+|-------------|---|------------------------|-----------|
+| 7.x         | → | 7.x                    | 7.17      |
+| 8.x         | → | 8.x                    | 8.x       |
+| main        | → | main                   |           |
 
 ## Development
 

docs/installation.asciidoc

@@ -38,6 +38,24 @@ gem 'elasticsearch', '~> 7.0'
 [discrete]
 === {es} and Ruby Version Compatibility
 
-The {es} client is compatible with currently maintained Ruby versions. We follow Ruby’s own maintenance policy and officially support all currently maintained versions per https://www.ruby-lang.org/en/downloads/branches/[Ruby Maintenance Branches].
-
-Language clients are forward compatible; meaning that clients support communicating with greater or equal minor versions of {es}. Elasticsearch language clients are only backwards compatible with default distributions and without guarantees made.
+The {es} client is compatible with currently maintained Ruby versions. We follow
+Ruby’s own maintenance policy and officially support all currently maintained
+versions per
+https://www.ruby-lang.org/en/downloads/branches/[Ruby Maintenance Branches].
+
+Language clients are forward compatible; meaning that clients support
+communicating with greater or equal minor versions of {es} without breaking. It
+does not mean that the client automatically supports new features of newer {es} 
+versions; it is only possible after a release of a new client version. For
+example, a 8.12 client version won't automatically support the new features of
+the 8.13 version of {es}, the 8.13 client version is required for that.
+{es} language clients are only backwards compatible with default distributions
+and without guarantees made.
+
+|===
+| Gem Version   |   | {es} Version | Supported
+
+| 7.x           | → | 7.x          | 7.17
+| 8.x           | → | 8.x          | 8.x
+| main          | → | main         |
+|===