Marcheur: XSLT-like Tree Processor Builder

Marcheur is a JavaScript library designed for building simplistic tree-walking and pattern-matching processors, drawing inspiration from XSLT 1.0's core algorithm. It allows developers to define rules for transforming tree structures, offering functionality analogous to XSLT without aiming to be a full replacement. The current stable version is 0.9.0, indicating it is pre-1.0 and its API may still be subject to changes. Due to the incomplete documentation (marked with 'XXX TDB' in the provided README excerpt), the release cadence is likely irregular, and the project's current development activity might be low. Its key differentiator is providing a lightweight mechanism for common tree transformation needs in JavaScript where full XSLT support is cumbersome or unavailable.