fix blockquote styling and tests for bold text rendering

[vsaase]

Fix blockquote inline formatting (bold, italic, links)

Blockquotes were ignoring inline styles — bold, italic, and link colors inside a > blockquote all rendered without their expected formatting.

Root cause: In MarkdownBuilder.visitText, the blockquote check short-circuited to styleSheet.blockquote instead of _inlines.last.style, discarding any styles accumulated by nested strong/em/a elements.

Changes:

builder.dart — _addParentInlineIfNeeded now seeds the inline element with the blockquote base style when inside a blockquote; visitText always uses _inlines.last.style (the accumulated style chain).
blockquote_test.dart — Updated the "should work with styling" test to assert correct bold/italic/link rendering; added a dedicated test for bold text inside a blockquote.

Note: this merge request was almost completely made with Claude and Github CoPilot

[jcpsantiago]

There's a nice reviewed fix at: https://github.com/jusbrasil/flutter_markdown_plus/pull/1/changes. Comparing both PRs, the one linked is neater (fewer code changes, no changes to deps).

FYI to the maintainers here.

[vsaase]

Your linked PR is shorter because it simply ignores stylesheet.blockquote