@csgrammar macro

[IssaHanou]

In HerbBenchmarks.PSB2_2021 I tested the merge_grammar function:

function merge_grammar(gs::Vector{ContextSensitiveGrammar})
    grammar_to_construct = ContextSensitiveGrammar()
    for g in gs
        for i in eachindex(g.rules)
            ex = :($(g.types[i]) = $(g.rules[i]))
            add_rule!(grammar_to_construct, ex)
        end
    end
    return grammar_to_construct
end

which originally had grammar_to_construct = @csgrammar begin end
and my tests were failing because a simple test failed because the grammar had 100 rules (like one of the problem grammars was included as well)

                test_g1 = @csgrammar begin
                    Rule = 1
                    Rule = Rule + Rule
                end
                test_g2 = @csgrammar begin
                    Rule = 2
                end
                test_g3 = @csgrammar begin 
                    Rule = 3
                end
                test_full_grammar = merge_grammar([test_g1, test_g2, test_g3])
                @test length(test_full_grammar.rules) == 4