fix(ocr_mkcontent): improve language detection and content formatting

[myhloli]

Motivation

Optimize the language detection logic to enhance content formatting. This
change addresses issues with long word segmentation. Language detection now uses a
threshold to determine the language of a text based on the proportion of English characters.
Formatting rules for content have been updated to consider a list of languages (initially
including Chinese, Japanese, and Korean) where no space is added between content segments
for inline equations and text spans, improving the handling of Asian languages.

The impact of these changes includes improved accuracy in language detection, better
segmentation of long words, and more appropriate spacing in content formatting for multiple
languages.

Modification

Please briefly describe what modification is made in this PR.

BC-breaking (Optional)

Does the modification introduce changes that break the backward compatibility of the downstream repositories?
If so, please describe how it breaks the compatibility and how the downstream projects should modify their code to keep compatibility with this PR.

Use cases (Optional)

If this PR introduces a new feature, it is better to list some use cases here and update the documentation.

Checklist

Before PR:

• Pre-commit or other linting tools are used to fix the potential lint issues.
• Bug fixes are fully covered by unit tests, the case that causes the bug should be added in the unit tests.
• The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
• The documentation has been modified accordingly, like docstring or example tutorials.

After PR:

• If the modification has potential influence on downstream or other related projects, this PR should be tested with those projects.
• CLA has been signed and all committers have signed the CLA in this PR.