Reduce accidental matches with max length setting

[ufukty]

Context

• While a user is editing, a rule can unexpectedly match across section boundaries, starting inside an incomplete section and extending until it finds the closing sequence of the next one.
• Dim already has one measure against accidental matches, which is brace balance checking. It's only effective for patterns that match sequences inside a scope and not across scopes.
• Rewrites the readme and changelog #57 added a mention of the intent to prevent accidental matches¹.

Problem

Rare accidental matches harm user experience.

Suggestion

• Prevent accidental matches by enforcing a limit on the maximum characters per match.
• Allow users to set per-rule limits and a default.
• Ignore matches that exceed the effective rule limit.
• The user configuration may look like this:

{
  "dim.rules": [
    { "pattern": "...", "max": 10 },
    { "pattern": "..." } // uses the default
  ],
  "dim.max": 100 // default
}

Considerations

Optional features:

• LoC limit.
• Language default for max.

Footnotes

1. "Dim ... to prevent eye irritation and performance problems that would arise when incomplete sections of code cause a rule to match into the next section's ending. (Experimental)" ↩