windowsdesktop-runtime-7.0: Add version 7.0.20

[RavenMacDaddy]

Now that v8 is both the regular and LTS version, it seems fitting to add v7 here — especially since some apps are built for this specific version and nothing else.

• [x] I have read the Contributing Guide.

[RavenMacDaddy]

/verify

[github-actions[bot]]

All changes look good.

Wait for review from human collaborators.

windowsdesktop-runtime-7.0

• [x] Description
• [x] License
• [x] Hashes
• [x] Checkver
• [x] Autoupdate
• [x] Autoupdate Hash Extraction

[github-actions[bot]]

All changes look good.

Wait for review from human collaborators.

windowsdesktop-runtime-7.0

• [x] Description
• [x] License
• [x] Hashes
• [x] Checkver
• [x] Autoupdate
• [x] Autoupdate Hash Extraction