Request docs cleanup: bring back TODOs section content as footnotes, etc.

[adamschwartz]

@ispivey please do what you can as discussed in chat, then assign to me for final touchups :)

[adamschwartz]

@ispivey Since it’s been a bit, decided to clean this up for now so that we’re not leaving cruft in there. Here’s the content that was there:

## TODO

- The “Random Notes” below need a home somewhere else, or a decision to punt.

### Random Constructor Notes

- If you expect Unicode values in your headers, URL- or Base64-encode your header values before adding them to a Headers object.

- `CF-Connecting-IP`: A Cloudflare specific header to specify the client IP

  - **Note:** Requests using the `GET` or `HEAD` methods cannot have a body.

  -  Valid `redirect` values:
    - `follow: boolean`: If a redirect reponse is returned to the fetch, another fetch will be fired based on the `Location` header in the response until a non-redirect code is returned. (i.e. `await fetch(..)` could never return a `301` redirect)
    - `manual: boolean`: redirect responses will return from a fetch

### Random `RequestInitCfProperties` object Notes

- `cacheTtl` <Type>number</Type>

  - This option forces Cloudflare to cache the response for this request, regardless of what headers are seen on the response. This is equivalent to setting two page rules: [“Edge Cache TTL”](https://support.cloudflare.com/hc/en-us/articles/200168376-What-does-edge-cache-expire-TTL-mean-) and [“Cache Level” (to “Cache Everything”)](https://support.cloudflare.com/hc/en-us/articles/200172266).

- `cacheTtlByStatus` <Type>{ [key: string]: number }</Type>

  - This option is a version of the `cacheTtl` feature which chooses a TTL based on the response’s status code. If the response to this request has a status code that matches, Cloudflare will cache for the instructed time, and override cache instructives sent by the origin. (e.g. `{ "200-299": 86400, 404: 1, "500-599": 0 }`) _Note - Cloudflare will still adhere to [standard cache levels](https://support.cloudflare.com/hc/en-us/articles/202775670-How-Do-I-Tell-Cloudflare-What-to-Cache-), so by default this will override cache behavior for static files. If you wish to cache non-static assets, you will need to set a [Cache Level of Cache Everything](https://support.cloudflare.com/hc/en-us/articles/200172266-What-do-the-custom-caching-options-mean-in-Page-Rules-) using a Page Rule._

- `resolveOverride` <Type>string</Type>

  - Redirects the request to an alternate origin server. You can use this, for example, to implement load balancing across several origins. (e.g.`us-east.example.com`). _Note - For security reasons, the hostname set in `resolveOverride` must be proxied on the same Cloudflare zone of the incoming request. Otherwise, the setting is ignored. CNAME hosts are allowed, so to resolve to a host under a different domain or a DNS only domain first declare a CNAME record within your own zone’s DNS mapping to the external hostname, set proxy on Cloudflare, then set resolveOverride to point to that CNAME record._

Please feel free to make PR which brings this stuff back as you feel is appropriate.

[ispivey]

Thank you!

[KimJ15]

Created MRK-13400 for future prioritization of an updated footnote experience. Closing this issue given how the supporting team determines bandwidth.