Support `#allow-multiple!` predicate to enable multiple content ranges

[pokey]

• Modify getTarget: Target field

  cursorless/packages/cursorless-engine/src/processTargets/modifiers/scopeHandlers/scope.types.ts

  Line 38 in 417e4f9

  getTarget(isReversed: boolean): Target;

  to getTargets(): Target[]
• Add predicate #allow-multiple! that sets a allowMultiple field on the node output
• When processing scopes in base tree sitter scope handler

  cursorless/packages/cursorless-engine/src/processTargets/modifiers/scopeHandlers/TreeSitterScopeHandler/BaseTreeSitterScopeHandler.ts

  Line 43 in 417e4f9

  .sort((a, b) => compareTargetScopes(direction, position, a, b));

  detect if there are multiple scopes with identical domains.
• If it happens, check the nodes for an allowMultiple field. If it exists, merge into one scope that has multiple content ranges. If it doesn't exist, throw an error saying they need to use the predicate if it was intentional