fix(typescript-estree): [ts 4.2] add support for import type equal declaration

[armano2]

typescript 4.2 introduced new missing syntax:

import type foo = require('bar');
export import type foo = require('bar');

AST addition

TSImportEqualsDeclaration <: Node {
  importKind: 'type' | 'value';
}

fixes #3183, ref babel/babel#12962, microsoft/TypeScript#41573

[typescript-eslint]

Thanks for the PR, @armano2!

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The core maintainers work on this in their personal time, so please understand that it may not be possible for them to review your work immediately.

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[codecov]

Codecov Report

Merging #3189 (541d17d) into master (7b6f2ab) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #3189   +/-   ##
=======================================
  Coverage   92.91%   92.91%           
=======================================
  Files         316      316           
  Lines       10808    10809    +1     
  Branches     3056     3057    +1     
=======================================
+ Hits        10042    10043    +1     
  Misses        342      342           
  Partials      424      424           

Flag	Coverage Δ
unittest	92.91% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
packages/typescript-estree/src/convert.ts	98.24% <100.00%> (+<0.01%)	⬆️

[bradzacher]

lgtm! Thanks
totally don't see the point of this syntax but whatever 🤷‍♂️

[dimitropoulos]

same, and, actually, if someone can explain why this syntax would ever actually be needed I'd benefit from (and, would appreciate) hearing why.

[armano2]

reason can be fond in this pr microsoft/TypeScript#41573