Improve detection of ASP and LP files

[nickswalker]

Add a pattern for Answer Set Programming.

Description

Answer Set Programming (#7184) was patternless, leading to false positives on LibrePCB .lp files (which don't appear popular enough for inclusion themselves). Now, it now matches files containing specific ASP directives (#include, #const, etc.). Because some ASP files won't have directives, it also looks for rules defined with :-, or lines simply containing "facts" (foo(x). or atom. or edge(2, 4).).

Added an additional ASP sample tohB.lp from Potassco's clingo repo (MIT licensed) to exercise the patterns.

Checklist:

• I am fixing a misclassified language
  • I have included a new sample for the misclassified language:
    • Sample source(s):
      • tohB.lp
    • Sample license(s): MIT
  • I have included a change to the heuristics to distinguish my language from others using the same extension.