fix: mdn#5287 by typechecking before calling string methods (mdn#5288)

build(deps-dev): bump html-validate from 6.2.0 to 6.3.2 (mdn#5296)

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build(deps): bump @mdn/browser-compat-data from 4.1.5 to 4.1.8 (mdn#5297

)

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Add support for 'spec-urls' frontmatter key (mdn#5284)

Fixes mdn#4704
Related: mdn#5277

This change adds support for listing specs in the Specifications section
based on the value of the 'spec-urls' frontmatter key — instead of or in
addition to listing specs based on the value of the 'browser-compat'
frontmatter key, or the value of the parameter passed to the
Specifications macro.

Add ability to draw diagram for inheritance chain of any length (mdn#…

…5261)

* Add triangle() function

* Improve lineWithTriangle() function

* Improve connectingLineWithTriangle() function

* Add calculateRectWidth() function

* Improve rectWithText() function

* Add ability to draw any number of rows

* Add test page

Make the Specifications macro not append the spec shortTitle (mdn#5283)

See discussion in w3c/browser-specs#517 (comment)

build(deps-dev): bump pytest from 7.0.0 to 7.0.1 in /deployer (mdn#5279)

build(deps-dev): bump pytest from 6.2.5 to 7.0.0 in /deployer (mdn#5257)

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build(deps-dev): bump black from 21.12b0 to 22.1.0 in /testing/integr…

…ation (mdn#5217)

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build(deps-dev): bump black from 21.12b0 to 22.1.0 in /deployer (mdn#…

…5219)

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