Update README to contains 4.2 release

Author: aaltat

README.rst

@@ -221,6 +221,7 @@ SeleniumLibrary 3.0 and 3.1         Selenium 2 and 3            Python 2.7 and 3
 SeleniumLibrary 3.2                 Selenium 3                  Python 2.7 and 3.4+         Drops Selenium 2 support.
 SeleniumLibrary 4.0                 Selenium 3                  Python 2.7 and 3.4+         Plugin API and support for event friging webdriver.
 SeleniumLibrary 4.1                 Selenium 3                  Python 2.7 and 3.5+         Drops Python 3.4 support.
+SeleniumLibrary 4.2                 Selenium 3                  Python 2.7 and 3.5+         Supports only Selenium 3.141.0 or newer.
 Selenium2Library 3.0                Depends on SeleniumLibrary  Depends on SeleniumLibrary  Thin wrapper for SeleniumLibrary 3.0 to ease transition.
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