Prepare release 0.6.4

[valar12]

Motivation

• Prepare a new release after merging the shortcut RelativePath regression tests.
• PowerShell Gallery publishing requires a module version that has not already been released.

Description

• Bumped ModuleVersion from 0.6.3 to 0.6.4.
• Added a 0.6.4 changelog entry for the new regression coverage.

Testing

• pwsh -NoLogo -NoProfile -Command 'Test-ModuleManifest -Path src/odscex.psd1 | Select-Object -ExpandProperty Version' returned 0.6.4.
• pwsh -NoLogo -NoProfile -Command '$PesterConfiguration = New-PesterConfiguration; $PesterConfiguration.Run.Path = "tests"; $PesterConfiguration.Run.Exit = $true; $PesterConfiguration.Output.Verbosity = "Detailed"; Invoke-Pester -Configuration $PesterConfiguration' - 20 passed
• git diff --check