Add support for `.properties` files in replexica i18n CLI

[maxprilutskiy]

Title: Add support for .properties files in replexica i18n CLI

What

Extend the replexica i18n CLI to handle .properties files for internationalization.

Why

• Many Java-based projects use .properties files for i18n
• Supporting this format will broaden our tool's usefulness
• It'll make it easier for e.g. Java devs to adopt our CLI

How

• Add a file parser for .properties format
• Implement conversion between .properties and our internal i18n format
• Update CLI commands to recognize and process .properties files
• Add unit tests for new functionality
• Update documentation to include usage with .properties files

[maxprilutskiy]

Resolved in #181