high-performance, selector-based, content-aware HTML template engine

Changes for 0.09 - 2023-08-04

• fix scoping of loops in sub-templates (i.e. 'replace_inner_template' or 'replace_outer_template' embedding a template that uses 'repeat_inner' or 'repeat_outer'); this could cause errors like "Use of uninitialized value in concatenation (.) or string at .../HTML/Blitz/CodeGen.pm line 387."