Open VSX: plugin listing text should not be selectable

[colin-grant-work]

Bug Description:

Steps to Reproduce:

1. Open the Extensions view
2. Search for e.g. git.
3. Try to select some text in one of the results.

Expected: no selection in the extensions view nodes.

Additional Information

• Operating System: RHEL7 (Electron)
• Theia Version: master

[vince-fugnitto]

The fix should be as simple as adding the noselect css class here:

theia/packages/vsx-registry/src/browser/vsx-extension.tsx

Line 419 in e91bea4

return <div className='theia-vsx-extension' data-for={tooltipId} data-tip={tooltip}>