Checklist:

• I have read freeCodeCamp's contribution guidelines.
• My pull request has a descriptive title (not a vague title like Update index.md)
• My pull request targets the master branch of freeCodeCamp.
• All the files I changed are in the same world language, for example: only English changes, or only Chinese changes, etc.

Related to PR #37912

This PR accomplishes the following:

• The result of The first commit includes all the transformations to MDX after executing @ojeytonwilliams' new mdx formatter script to the Chinese curriculum files. The results include tweaks to final version of about 10 files that did not properly convert.
• Added the 77 challenges that were in English but did not exist in the Chinese folder.
• Corrected the incorrect syntax for strong tags for over 50 challenges. It mainly affected the project user stories in the Responsive Web Design section. It also fixed the Notes that are in various challenges' description and instructions sections.

This PR must be merged before @miyaliu666 and/or the Chinese translation team can start fully translating 77 challenges that are new to the Chinese curriculum and a handful of challenges that need a partial or full translation as the first step in the Chinese curriculum audit process.