[Feature] Add remove_eol_characters hook

[C1rN09]

This PR adds a new script/pre-commit-hook, named remove-improper-eol-in-cn-docs.

The script aims at resolving extra whitespaces in Chinese docs, which is a long-standing HTML issue as discussed here.

To solve the issue, this script finds and removes end_of_line characters which split natural Chinese paragraphs. For example,

这是一个，
像诗一样的
测试

will be changed to

这是一个，像诗一样的测试

However, the following cases stay unchanged:

• Docs written in English

This is,
a poem-like
test

• Natural paragraphs (split by 2+ eol characters in Markdown)

这是一个

测试

[zhouzaida]

Please add the hook in https://github.com/open-mmlab/pre-commit-hooks/blob/master/README.md#hooks-available

[C1rN09]

Tested with the following config in MMEngine

- repo: https://github.com/C1rN09/pre-commit-hooks.git
    rev: 02421bc
    hooks:
      - id: check-copyright
        args: ["mmengine", "tests"]
      - id: remove-improper-eol-in-cn-docs

Seems good.