[prakriya] Fix various small UX issues

[akprasad]

• Fix typos in णिजन्ते, यङन्ते
• Add filtering support for the dhatu text or meaning.
• Add support for Devanagari, SLP1, and HK in the filter.
• Hide the unused कृदन्तानि / सुबन्तानि tabs since they don't do anything.
• Open header links in a new tab (since the back button doesn't work with this demo).
• Scroll to top when displaying a dhatu's forms (see GH #30).
• Remove duplicates (e.g. if a cell has baBUva twice due to an optional rule that had no impact on the outcome.)
• Remove extra console.log statements.