fix: image preview display error when image.alt includes '<' or '>'

[PENEKhun]

Description

Describe the bug

When specifying a preview image in a post,
if you specify a value of < or > for alt, the image will not display properly because it encroaches on the HTML tag range.

To Reproduce

1. Create a new post.
2. In the post properties, write image.alt to contain < or >, as follows

• example

image:
  path: /commons/devices-mockup.png
  alt: get device image -> show mockup

Expected behavior && Logs/Screenshots

• At Home (root path)

• At Post

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Improvement (refactoring and improving code)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

Additional context

How has this been tested

• I have run bash ./tools/test (at the root of the project) locally and passed
• I have tested this feature in the browser

[cotes2020]

It would be better to use Jekyll's xml_escape filter.

[PENEKhun]

thanks you for suggestion.