TRP.js v0.3.1 release draft

[athewsey]

Issue #, if available: #154, #158

Description of changes:

• (Bugfix) Suppress unnecessary "content may be truncated" warnings when Textract API NextToken is present but null, and enable proper warning when NextToken is present for multi-page constructor TextractDocument([resp1, resp2, ...])
• (Bugfix) Fix ApiTableCellEntityType enumerations of TABLE_FOOTER and TABLE_SECTION_TITLE values

Testing:

• Unit tests expanded to cover fixed cases
• Test build available on NPM at v0.3.1-alpha.2 - feedback appreciated!

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[athewsey]

No recent feedback from alpha testers, so merging and releasing these fixes to main