Documentation: incorrect code pattern in feature_advanced_keycodes.md

[dloidolt]

Issue Description

The feature_advanced_keycodes.md has this part:

To check that only a specific set of mods is active at a time, AND the modifier state and your desired mod mask as explained above and compare the result to the mod mask itself: get_mods() & <mod mask> == <mod mask>.

For example, let's say you want to trigger a piece of custom code if one-shot left control and one-shot left shift are on but every other one-shot mods are off. To do so, you can compose the desired mod mask by combining the mod bits for left control and shift with (MOD_BIT(KC_LCTL) | MOD_BIT(KC_LSFT)) and then plug it in: get_oneshot_mods() & (MOD_BIT(KC_LCTL) | MOD_BIT(KC_LSFT)) == (MOD_BIT(KC_LCTL) | MOD_BIT(KC_LSFT)). Using MOD_MASK_CS instead for the mod bitmask would have forced you to press four modifier keys (both versions of control and shift) to fulfill the condition.

However the pattern get_mods() & <mod mask> == <mod mask> does not check if only a specific set is active at a time. This expression is also true when a mod is pressed together with the specific mod.
I think the correct pattern is get_mods() == <mod mask>

I am not a QMK expert, but something I noticed with the first code example in feature_advanced_keycodes.md: should the first code example be implemented with Key Overrides?

[filterpaper]

This expression is also true when a mod is pressed together with the specific mod.

Do you mean that when Left Ctrl + Shift is held together, the following is true?

get_mods() & MOD_MASK_SHIFT == MOD_MASK_SHIFT