@signpdf/* 3.1.0

• [utils] Added SIG_FLAGS and ANNOTATION_FLAGS to improve readability;
• [utils] Reworked findByteRange to match in more cases where it was incompatible so far (it didn't allow optional spaces in the array).
• [placeholder-pdfkit010] Uses SIG_FLAGS and ANNOTATION_FLAGS instead of magic numbers;
• [placeholder-pdfkit010] Allow passing in widgetRect to override the default [0, 0, 0, 0] one;
• [placeholder-plain] Allow passing in widgetRect to override the default [0, 0, 0, 0] one;
• [placeholder-pdf-lib] Introduce the package that uses PDF-LIB for adding a placeholder;
• [signpdf] Use the BR position findByteRange provides to spare a search for it;
• [signpdf] Reexports the Signer base (abstract) class and SignPdfError;
• [examples] Introduce an example that provides a visible widget (implemented with pdfkit);
• [examples] Introduce a placeholder-pdf-lib example;
• Bumped version of axios;