Escaped `:` in `.properties` causes invalid URLs in generated `.yaml`

[SableRaf]

Description

The Gradle task writeLibraryProperties (in processing-library-template) correctly escapes : in .properties files (e.g. https\://...) per the file format spec. However, the parse_and_validate_properties_txt.py script in this repository does not unescape these values before writing them to .yaml.

As a result, URLs appear broken in the Contribution Manager.

Expected behavior

Escape sequences like \: should be unescaped when converting .properties to .yaml.

Suggested fix

Update the parse_text() function to unescape escaped characters such as \: before validation and output.

Related to prior conversation in processing/processing-library-template#88