Add a DocxScript enum (Script alias) and a script field on DocxRun to
raise or lower text off the baseline — for exponents (x2), chemical
formulas (H2O), ordinals and footnote markers.

- DOCX: renders as the <w:vertAlign> run property
- PDF: smaller glyphs with a baseline shift (text-rise operator)
- Reader: <w:vertAlign> parsed back for full read/modify/write round-trip
- README + example + CHANGELOG; bump to 1.4.0
- format pre-existing files to satisfy the new CI format gate