Add a page for common checksum issues and troubleshooting

## What New Or Updated Would You Like To See?

A page for common checksum issues and troubleshooting steps.

## Why Is It Needed?

When a file download fails the checksum check, it would be good for users to be able to find more details about possible causes and help them correct the issues. Currently searching for checksum on the docs page turns up just references to the PowerShell helper and the Community Repository rules regarding checksums.

## Additional Context?

I see this page as potentially being a good addition to the errors around checksums, to be able to enhance the error messages without making too much needing to be in Chocolatey CLI.

Start by reviewing the existing checksum references in the docs, including the PowerShell helper and Community Repository rules. Define the common failure causes and troubleshooting steps, then add a discoverable page whose content helps users correct failed checksum checks.

Written by the indexing model from the issue text.