fix: matching of Italic nested within Bold (and avoid crash)

[pavel-lens]

What does this PR do?

https://lenster.xyz/posts/0x5b8b-0x076f

Render of this post crashes, because it contains string "ENS" which is an Italic nested within Bold and the Regex matches don't work out properly, leaving unclosed <mdItalic2> tag which then corrupts rendered XHML.

Fixes #1187

Type of change

• Bug fix (non-breaking change which fixes an issue)

How should this be tested?

• Test A: Open https://lenster.xyz/posts/0x5b8b-0x076f on main branch
• Test B: Open post in current branch

Checklist

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Name	Status	Preview	Updated
lenster	✅ Ready (Inspect)	Visit Preview	Nov 13, 2022 at 3:45PM (UTC)

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[foolo]

@svitekpavel The solution works, but i think it created some new warnings :)

[bigint]

@foolo we had this for long 😕

RN we are trying to migrate to lexical #1188 so the editor and renderer will be same