exercises(pangram): test more non-alphanumeric printable ASCII

[MatthijsBlom]

This test checks that the submitted solution does not panic on non-alphanumeric input.

Faulty solution 'from the wild' that is caught by this test but not by the others:

pub fn isPangram(str: []const u8) bool {
    var seen = std.bit_set.StaticBitSet('z' - 'a' + 1).initEmpty();
    for (str) |c| {
        const index = std.math.sub(u8, std.ascii.toLower(c), 'a') catch continue;
        // if  c > 'z'  then  index > 25  😱
        seen.set(index);  // panics when  index >= 26
    }
    return ~seen.mask == 0;
}

There are no test cases in problem-specifications that could be pulled in to the same effect. I will not myself pursue upstreaming into problem-specifications.

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[ee7]

Somewhat similar test cases were rejected or removed upstream in the past:

• pangram: Remove non-ascii test cases. problem-specifications#440
• pangram: rework tests (discussion) problem-specifications#893

However, in this case I'm inclined to merge. It's true that the existing non-alphanumeric printable ASCII characters in the tests are sufficiently close to 'a' and 'z' to not cause a panic for an implementation similar to the one given. Thanks for the contribution.