Update supported details for 7.x (#1419)

* Update supported versions

* Slight reword to clarify node 10 is (just) minimum

Author: shadowspawn

Readme.md

@@ -865,8 +865,8 @@ More samples can be found in the [examples](https://github.com/tj/commander.js/t
 
 ## Support
 
-The current version of Commander is fully supported on Long Term Support versions of Node, and is likely to work with Node 6 but not tested.
-(For versions of Node below Node 6, use Commander 3.x or 2.x.)
+The current version of Commander is fully supported on Long Term Support versions of node, and requires at least node v10.
+(For older versions of node, use an older version of Commander. Commander version 2.x has the widest support.)
 
 The main forum for free and community support is the project [Issues](https://github.com/tj/commander.js/issues) on GitHub.
 

SECURITY.md

@@ -6,10 +6,13 @@ Old versions receive security updates for six months.
 
 | Version | Supported                                  |
 | ------- | ------------------------------------------ |
+| 7.x     | :white_check_mark: |
 | 6.x     | :white_check_mark: support ends 2021-30-06 |
 | 5.x     | :white_check_mark: support ends 2021-01-20 |
 | < 5     | :x:                                        |
 
+Pull Requests for security issues will be considered for older versions back to 2.x.
+
 ## Reporting a Vulnerability
 
 To report a security vulnerability, please use the