Draft: Add file and update_file method to gitee client

What does this MR do and why?

Add file and update_file method to gitee client.

Usage

client = Gitee::Client.new(gitee_access_token: <gitee_access_token>)


# get file from default branch

client.file(repo_path, file_path)

# get file from `xxx` branch

client.file(repo_path, file_path, 'xxx')

# update file
# content: the new file content
# sha: the sha get by `client.file`
# message: commit message

# get file from default branch
client.update_file(repo_path, file_path, content, sha, message)

# get file from 'xxx' branch
client.update_file(repo_path, file_path, content, sha, message, 'xxx')

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.