Superfile doesn't render small text files

[jkrshnmenon]

Describe the bug
The function isTextFile in src/internal/string_function.go returns false even if the file contains printable characters only.

To Reproduce
Steps to reproduce the behavior:

1. Create a file with the command echo "A" > /tmp/test
2. Use spf to open the /tmp directory and seek to the test file
3. The pane on the right will show the Unsupported formats error

Expected behavior
A normal rendering of the file contents

System information (please complete the following information):

• OS: Ubuntu
• Version 22.04
• Superfile Version v1.1.3

[jkrshnmenon]

Screenshots

Fixed the screenshot

[jkrshnmenon]

I believe the reason for this behavior is that this line will iterate beyond the contents of the file and stop when it encounters the first NULL byte.

A simple fix could be something like the following:

    fileInfo, err := file.Stat()
    if err != nil {
	return false, err
    }
    
    bufferSize := min(fileInfo.Size(), 1024)

    reader := bufio.NewReader(file)
    buffer := make([]byte, bufferSize)