Docs: replace stale AppVeyor build references with branch-specific GitHub Actions artifact links

[Copilot]

The README's "Current development builds" guidance pointed users to deprecated AppVeyor paths and did not clearly distinguish where to get artifacts for master vs development. This updates build documentation to the current GitHub Actions workflow views that expose downloadable artifacts for each branch context.

• What changed

  • Removed outdated AppVeyor references from the README header/status area.
  • Updated build badge/linking to GitHub Actions for master.
  • Renamed Current development builds section to Latest Builds to accurately reflect that it covers both branches.
  • Rewrote the section description to: "You can download the latest successful builds of the current master and development branches from the GitHub Actions > Artifacts section following the links below."
  • Replaced the bullet list with a markdown table that includes per-branch SVG shield status badges, linked branch names, and direct artifact download links with emoji.

• Resulting docs behavior

  • Users land on filtered workflow-run lists that map to the correct branch flow and can open runs to download artifacts from the Artifacts section.
  • Reduces ambiguity between stable (master) and in-flight (development) build outputs.
  • The table format makes it immediately clear which badge and artifact link corresponds to which branch.

• Snippet (updated README section)

  ## Latest Builds
  
  You can download the latest successful builds of the current [`master`](https://github.com/cmderdev/cmder/tree/master) and [`development`](https://github.com/cmderdev/cmder/tree/development) branches from the **GitHub Actions > Artifacts** section following the links below:
  
  | Branch | Build Status | Download Artifacts |
  |--------|-------------|-------------------|
  | 🔒 [`master`](https://github.com/cmderdev/cmder/tree/master) | [![master build status](https://github.com/cmderdev/cmder/actions/workflows/build.yml/badge.svg?branch=master)](…) | [📦 Artifacts](…) |
  | 🔧 [`development`](https://github.com/cmderdev/cmder/tree/development) | [![development build status](https://github.com/cmderdev/cmder/actions/workflows/build.yml/badge.svg?branch=development)](…) | [📦 Artifacts](…) |

[Copilot]

Pull request overview

Updates the README build documentation to remove deprecated AppVeyor references and direct users to the correct GitHub Actions workflow run lists for downloading build artifacts, distinguishing master push builds from development PR-targeted builds.

Changes:

• Removed AppVeyor build status badge/reference from the README header.
• Updated the build badge/link to point to GitHub Actions master push runs.
• Rewrote “Current development builds” to include explicit GitHub Actions links for successful master and development build artifacts.

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