Add documentation expanding on SceneGraph/BrightScript performance considerations - #80

[brightscript-fence-required] bare ``` fence with BrightScript content; tag it as ```brightscript (sub keyword, end sub, m.top/global/video)

[brightscript-fence-required] bare ``` fence with BrightScript content; tag it as ```brightscript (sub keyword, end sub, CreateObject("ro..."))

[brightscript-fence-required] bare ``` fence with BrightScript content; tag it as ```brightscript (sub keyword, end sub, CreateObject("ro..."))

[brightscript-fence-required] bare ``` fence with BrightScript content; tag it as ```brightscript (m.top/global/video, m.field assignment, m.field.method() call)

[brightscript-fence-required] bare ``` fence with BrightScript content; tag it as ```brightscript (endif, m.top/global/video, m.field assignment)

[brightscript-fence-required] bare ``` fence with BrightScript content; tag it as ```brightscript (sub keyword, end sub, m.field assignment)

[brightscript-fence-required] bare ``` fence with BrightScript content; tag it as ```brightscript (m.top/global/video, m.field.method() call, m. field reference)

[brightscript-fence-required] bare ``` fence with BrightScript content; tag it as ```brightscript (ro-prefixed object)

[brightscript-fence-required] bare ``` fence with BrightScript content; tag it as ```brightscript (CreateObject("ro..."), ro-prefixed object, CreateObject assignment)

[brightscript-fence-required] bare ``` fence with BrightScript content; tag it as ```brightscript (ro-prefixed object)

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, actions/setup-node@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

[html-blank-between-tags] blank line between tags inside HTML table (breaks GitHub/IDE preview)

[html-blank-in-cell] blank line inside HTML table cell content (breaks GitHub/IDE preview) — replace with <br /> or restructure

[html-blank-in-cell] blank line inside HTML table cell content (breaks GitHub/IDE preview) — replace with <br /> or restructure

[html-blank-in-cell] blank line inside HTML table cell content (breaks GitHub/IDE preview) — replace with <br /> or restructure

[html-blank-in-cell] blank line inside HTML table cell content (breaks GitHub/IDE preview) — replace with <br /> or restructure

[html-blank-between-tags] blank line between tags inside HTML table (breaks GitHub/IDE preview)

[html-blank-between-tags] blank line between tags inside HTML table (breaks GitHub/IDE preview)

[html-blank-between-tags] blank line between tags inside HTML table (breaks GitHub/IDE preview)

[html-blank-between-tags] blank line between tags inside HTML table (breaks GitHub/IDE preview)