…935) (#936)

* test: add failing regression tests for issue #935 (abbreviation + emphasis)

* fix: AbbreviationParser now substitutes post-inline-parse, fixes emphasis corruption (#935)

The PostMatch hook approach (running mid-parse) produced a ContainerInline
with IsClosed=false that disrupted FindLastContainer(), causing emphasis
delimiters to be appended as children of the abbreviation container instead
of as root siblings. It also had an off-by-one (i != 0 vs i != content.Start)
that caused abbreviations to be missed when the literal started inside emphasis.

Replace with a document.ProcessInlinesEnd handler that walks the fully resolved
inline tree (after EmphasisInlineParser and LinkInlineParser have run), inserting
AbbreviationInline/LiteralInline siblings directly into parent containers without
any wrapper ContainerInline.

Also update TestSourcePosition.TestAbbreviations to reflect the new tree shape
(no container wrapper; empty leading literals at word boundaries are pruned).

Fixes #935

Introduces AllowNestedAlerts on AlertExtension and AlertInlineParser
(default: false) to allow alert blocks inside blockquotes or list items.

The UseAlertBlocks() pipeline extension method exposes the new option
via an allowNestedAlerts parameter.

Resolves #853

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

* Update readme with Alert extension details

* Update readme.md

Co-authored-by: Miha Zupan <mihazupan.zupan1@gmail.com>

---------

Co-authored-by: Alexandre Mutel <alexandre_mutel@live.com>
Co-authored-by: Miha Zupan <mihazupan.zupan1@gmail.com>