Add isRenderedTextFile and hasRenderedText detection functions

[Copilot]

Adds detection for pages displaying rendered markup content (markdown, textile, rdoc, org, creole, mediawiki, wiki, rst, asciidoc, pod) as specified in GitHub's markup gem.

Changes

• isRenderedTextFile(url): Detects single file pages with rendered text extensions

  • Matches against: .md, .markdown, .mdown, .mkdn, .textile, .rdoc, .org, .creole, .mediawiki, .wiki, .rst, .asciidoc, .adoc, .asc, .pod
  • Case-insensitive extension matching

• hasRenderedText(url): Composite detection for pages with rendered text

  • Returns true for repository root (README display) or rendered text files
  • Intentionally excludes SVG and other rendered content

Usage

import { isRenderedTextFile, hasRenderedText } from 'github-url-detection';

// Detect rendered text file
isRenderedTextFile(new URL('https://github.com/user/repo/blob/main/README.md')) // true
isRenderedTextFile(new URL('https://github.com/user/repo/blob/main/file.svg')) // false

// Detect any page with rendered text
hasRenderedText(new URL('https://github.com/user/repo')) // true (repo root)
hasRenderedText(new URL('https://github.com/user/repo/blob/main/docs.rst')) // true

Original prompt

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This section details on the original issue you should resolve

<issue_title>hasRenderedText (markdown etc)</issue_title>
<issue_description>```js
export const isRenderedTextFile = isSingleFile && endsWith(md)
export const hasRenderedText = isRepoRoot || isRenderedTextFile || etc

These shouldn't include SVG and other rendered content

Partially implemented in https://github.com/refined-github/refined-github/pull/4151/files#diff-a1b04b00ad1bdc63f8898dfbf43b2faf61ae3be4f50182d5a144d3e7f0dc7c29R14</issue_description>

<agent_instructions>The test is effectively /\.(textile|rdoc|org|creole|(media)?wiki|rst|a(scii)?doc|asc|pod)$/.test(location.pathname) but include markdown extensions.

origin: https://github.com/github/markup/blob/2b0e7f216904253092c90754cd95aac6d499583d/README.md</agent_instructions>

## Comments on the Issue (you are @copilot in this section)

<comments>
</comments>

• Fixes hasRenderedText (markdown etc) #148

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