Rephrase sentence. Separate two sentences with period.

Replace
```
WebDriver drives a browser natively ..., marks a leaps forward
```
with
```
WebDriver drives a browser natively .... It marks a leaps forward
```

I claim the version before the change is a 'run-on sentence', i.e.
two separate sentences that are connected improperly (see
https://academicguides.waldenu.edu/writingcenter/grammar/runonsentences).

This commit changes how those two sentences are connected; in
particular, it separates the sentences with a period and provides a
subject for the second sentence.

Author: zipperer

website_and_docs/content/documentation/webdriver/_index.en.md

@@ -9,8 +9,8 @@ aliases: ["/documentation/en/webdriver/"]
 
 
 WebDriver drives a browser natively, as a user would, either locally
-or on a remote machine using the Selenium server,
-marks a leap forward in terms of browser automation.
+or on a remote machine using the Selenium server.
+It marks a leap forward in terms of browser automation.
 
 Selenium WebDriver refers to both the language bindings
 and the implementations of the individual browser controlling code.