Add dedicated docs for innerHTML and textContent

[amirhhashemi]

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• This PR references an issue (except for typos, broken links, or other minor problems)

Description(required)

innerHTML and textContent are documented on the same page, which may lead to some issues:

1. They serve different purposes, and placing them together could be misleading. The title of the page separates the two with "or," suggesting they are equivalent, when in fact they are not. Additionally, using innerHTML has certain security implications that should be considered.
2. This arrangement disrupts the consistency of the API reference docs. Unrelated topics should not be documented on the same page.
3. Some users might be looking specifically for information about innerHTML, as it is more widely used. Including information about textContent can create unnecessary friction.
4. I found that innerText is not documented either. Should we also add its docs to the same page?

Furthermore, there were a few issues with the content itself:

1. The first two sentences are unclear and confusing:

   "These work the same as their property equivalent. Set a string and they will be set."

2. The example provided was not useful, so I removed it.

This PR addresses these issues. Additionally, I updated the the legacy routes redirector middleware to redirect to the innerHTML page. This further highlights the problem of documenting multiple concepts on one page, as it limits our control over the URLs.

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