Enable the no-nested-ternary ESLint rule in the web/ directory

[Snuffleupagus]

This rule is already enabled in mozilla-central, and helps avoid some confusing formatting[1], see https://searchfox.org/mozilla-central/rev/a92ed79b0bc746159fc31af1586adbfa9e45e264/tools/lint/eslint/eslint-plugin-mozilla/lib/configs/recommended.js#209-210

Since some cases may not be aren't entirely straightforward to convert, and some we probably don't want to change either[2], this patch is limited to the web/ directory as a proof-of-concept.

Please find additional details about the ESLint rule at https://eslint.org/docs/rules/no-nested-ternary

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[1] One example with three ternary statements:

pdf.js/src/core/fonts.js

Lines 2623 to 2630 in 93aa613

	var stackDelta =
	op <= 0x8e
	? TTOpsStackDeltas[op]
	: op >= 0xc0 && op <= 0xdf
	? -1
	: op >= 0xe0
	? -2
	: 0;

[2] One example that should be whitelisted:

pdf.js/src/core/jbig2.js

Lines 82 to 92 in 93aa613

	var value = readBits(1) ?
	(readBits(1) ?
	(readBits(1) ?
	(readBits(1) ?
	(readBits(1) ?
	(readBits(32) + 4436) :
	readBits(12) + 340) :
	readBits(8) + 84) :
	readBits(6) + 20) :
	readBits(4) + 4) :
	readBits(2);

[timvandermeij]

/botio-linux preview

[pdfjsbot]

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[pdfjsbot]

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[timvandermeij]

I agree with the decision at mozilla-central for enabling this since I also found the nested ternary statements harder to read than the new structure. Thanks!

[Snuffleupagus]

[...] since I also found the nested ternary statements harder to read than the new structure.

At least to my eye, the recent introduction of Prettier actually made some of these cases even less readable than before since any helpful indentation is now forbidden. That's actually what prompted me to start looking into this now, however a full conversion may take some time since it's not always clear immediately what the best solution is (and some cases we'll want to whitelist).

Also, we used to have loads of these nested ternary statements in the Colourspace/Image code, but converting that code to use Uint8ClampedArray got rid of most of those; thanks for landing this!