PR into master from dev/olga/4417-support-underline-in-text-mode-v3

[OlgaRedozubova]

branch: dev/olga/4417-support-underline-in-text-mode-v3

Why:

Fixes MMD: support \underline in text mode #4417

What's being changed:

Added support to underline in text mode.

• Underline text: \underline{Underlined text!}

• Underline text: \uline{Underlined text!}

  

• Double underline text: \underline{\underline{Double underlined text!}}

• Double underline text: \uuline{Double underlined text!}

  

• Wavy underlined text: \uwave{This text is underlined with a wavy line!}

  

• Dashed underline text: \dashuline{Dashed Underline}

• Dotted underline text: \dotuline{Dotted Underline}

  

• Strikethrough text: \sout{Text with a horizontal line through its center!}

• Struck with Hatching text: \xout{Text with hatching pattern!}

  

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TODO: Add README about latex underline