Support Zettelkasten Filenames

[smtucker]

Description:

This PR adds a feature to improve how note titles are displayed in the Perlite file explorer. It introduces an optional setting that allows Perlite to use a note's frontmatter title field or its first H1 heading as the display title, falling back to the filename only if neither is present.

Problem Solved (Why):

Users employing Zettelkasten or similar systems often prefix filenames with UIDs (e.g., 202305151000_actual_note_title.md). While useful for organization, these UIDs can make the file explorer view feel cluttered. This feature provides a cleaner, more readable experience, allowing Perlite to align with title display behavior in some plugins used in Obsidian and Neovim.

Changes Implemented (How):

• A new environment variable is introduced to control this title display behavior.
• A new function has been added to helper.php responsible for resolving the preferred display title according to the new logic.
• The existing menu function in helper.php has been refactored to incorporate this new title resolution when the feature is enabled.