Auto merge of #23943 - georgeroman:implement_take_element_screenshot_wd_command, r=jdm

Implement TakeElementScreenshot WebDriver command

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Cargo.lock

@@ -5491,6 +5491,7 @@ dependencies = [
  "serde_json 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "servo_config 0.0.1",
  "servo_url 0.0.1",
+ "style_traits 0.0.1",
  "url 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "uuid 0.7.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "webdriver 0.40.1 (registry+https://github.com/rust-lang/crates.io-index)",