Element text selector: Normalize whitespace

[ftes]

Goal: Make it easier to find an element by text (element/3, has_element?/3) if there is nested markup.

Example input:

<span>
  Text
  <span>with whitespace</span>
</span>

Status quo:

• element(view, "span", "Text\n with whitespace")
• element(view, "span", ~r/Text\n.*with whitespace/)

With this PR:

• element(view, "span", "Text with whitespace")

Solution: Normalize whitespace (convert different whitespace characters to regular space, collapse consecutive whitespace).

Breaking change: This PR changes the default behaviour. Maybe this should be opt-in instead?

Pointers

To feature test libraries, which of course can't be compared 1:1.

Wallaby

Matches any element by its inner text.
~s{.//*[contains(normalize-space(text()), "#{selector}")]}
xpath.ex
https://developer.mozilla.org/en-US/docs/Web/XPath/Functions/normalize-space

Playwright

Matching by text always normalizes whitespace, even with exact match. For example, it turns multiple spaces into one, turns line breaks into spaces and ignores leading and trailing whitespace.
https://playwright.dev/docs/locators#get-by-text