Add required Impression and MediaFile/@delivery to Tremor VAST 2.0 samples

[aleksUIX]

Summary

Fixes #45. Two Tremor VAST 2.0 files did not validate against vast_2.0.1.xsd:

• vast2Nonlinear.xml: 10 <InLine> ads, no <Impression> on any of them (minOccurs=1)
• vast2VPAIDLinear.xml: same missing <Impression>, plus the SWF <MediaFile> omitted required @delivery

These are the only version="2.0" files in the repo that failed that schema. The rest of the Tremor 2.0 set already has both fields. vast2RegularLinear.xml in the same folder is the model: Impression immediately after AdTitle, delivery="progressive" on MediaFile.

Fix

Copied that sibling Impression (including id="blah" and the existing ScanScout CDATA URL) onto every InLine in the two files. Added delivery="progressive" on the VPAID SWF. No other edits: creative URLs, companions, and ad ids are unchanged.

Test plan

Against vast_2.0.1.xsd:

xmllint --noout --schema vast_2.0.1.xsd \
  "VAST 1-2.0 Samples/Tremor-Video-Samples/vast2Nonlinear.xml" \
  "VAST 1-2.0 Samples/Tremor-Video-Samples/vast2VPAIDLinear.xml"

• both files now validate
• sibling vast2RegularLinear.xml still validates
• all 13 version="2.0" XML files in this repo validate; 0 failures

Closes #45