Delimiter runs with punctuation on both sides are rejected

[Gabriella439]

The minimal reproduction is that the string *.*. fails to parse:

ghci> MMark.parse "" "*.*."
Left (ParseErrorBundle {bundleErrors = FancyError 2 (fromList [ErrorCustom (NonFlankingDelimiterRun ('*' :| ""))]) :| [], bundlePosState = PosState {pstateInput = "*.*.", pstateOffset = 0, pstateSourcePos = SourcePos {sourceName = "", sourceLine = Pos 1, sourceColumn = Pos 1}, pstateTabWidth = Pos 4, pstateLinePrefix = ""}})

A non-minimal reproduction that conveys the actual problem I'm grappling with is that the following markdown fails to parse:

1. **API (Application Programming Interface)**: A set of protocols and tools for building and interacting with software applications.
2. **CI/CD (Continuous Integration/Continuous Deployment)**: Practices that enable developers to frequently integrate code into a shared repository and deploy updates swiftly and safely.
3. **OAuth (Open Authorization)**: An open standard for token-based authentication and authorization on the internet.
4. **UX (User Experience)**: The overall experience a person has when interacting with a product, particularly in terms of how easy and enjoyable it is to use.

The problem is that for each bolded "heading" the end of the heading is )**: which is a delimiter run with punctuation on both sides, which the mmark package rejects.

I wasn't sure if this rejection was intentional (because I know this package tries to reject some things intentionally to avoid common errors) so I wasn't sure whether to report this as a bug I wanted to ask about it just in case.

[mrkkrp]

Similar to #114 the solution is the same—simply escape the closing parenthesis with a backslash.