docs: add info about dev and runtime requirements (#1540)

Ref #1532

Author: char0n

README.md

@@ -40,6 +40,11 @@ We'll be consolidating that soon. Just giving you the heads up. You may see refe
 - [Graveyard](docs/migration/graveyard-3-x.md)
 - [Migration guide](docs/migration/migration-2-x-to-3-x.md)
 
+### Runtime 
+
+- Node.js `>=` 10.x
+- `swagger-client` works in the latest versions of Chrome, Safari, Firefox, and Edge.
+
 ## Security contact
 
 Please disclose any security-related issues or vulnerabilities by emailing [[email protected]](mailto:[email protected]), instead of using the public issue tracker.

docs/development/setting-up.md

@@ -5,9 +5,11 @@
 - git, any version
 - NPM 6.x
 
-Generally, we recommend following guidelines from [Node.js Releases](https://nodejs.org/en/about/releases/) to only use Active LTS or Maintenance LTS releases.
+Generally, we recommend following guidelines from [Node.js Releases](https://nodejs.org/en/about/releases/) to only use `Current`, `Active LTS` or `Maintenance LTS` releases.
 
-**Building**
+Current Node.js:
+- Node.js 14.x
+- NPM 6.x
 
 Current Node.js Active LTS:
 - Node.js 12.x
@@ -17,14 +19,6 @@ Current Node.js Maintenance LTS:
 - Node.js 10.x
 - NPM 6.x
 
-Unsupported Node.js LTS that should still work:
-- Node.js 8.13.0 or greater
-- NPM 6.x
-
-**Runtime**
-
-- Node.js `>=`4.x
-- `>=`ES5 compatible web browsers, IE11+
 
 ### Steps