BIP360: Pay to Merkle Root (P2MR) (#1670)

Review comments and assistance by:
  Armin Sabouri <armins88@gmail.com>
  D++ <82842780+dplusplus1024@users.noreply.github.com>
  Jameson Lopp <jameson.lopp@gmail.com>
  jbride <jbride2001@yahoo.com>
  Joey Yandle <xoloki@gmail.com>
  Jon Atack <jon@atack.com>
  Jonas Nick <jonasd.nick@gmail.com>
  Kyle Crews <kylecrews@Kyles-Mac-Studio.local>
  Mark "Murch" Erhardt <murch@murch.one>
  notmike-5 <notmike-5@users.noreply.github.com>
  Vojtěch Strnad <43024885+vostrnad@users.noreply.github.com>

Co-authored-by: Ethan Heilman <ethan.r.heilman@gmail.com>
Co-authored-by: Isabel Foxen Duke <110147802+Isabelfoxenduke@users.noreply.github.com>

bip-0360/ref-impl/js/.gitignore

@@ -0,0 +1,76 @@
+# Dependencies
+node_modules/
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+pnpm-debug.log*
+lerna-debug.log*
+
+# Build outputs
+dist/
+build/
+*.tsbuildinfo
+
+# TypeScript
+*.js.map
+*.d.ts.map
+
+# Environment variables
+.env
+.env.local
+.env.*.local
+
+# IDE / Editor files
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+.DS_Store
+
+# OS files
+Thumbs.db
+desktop.ini
+
+# Testing
+coverage/
+.nyc_output/
+*.lcov
+
+# Logs
+logs/
+*.log
+
+# Temporary files
+*.tmp
+*.temp
+.cache/
+
+# Optional npm cache directory
+.npm
+
+# Optional eslint cache
+.eslintcache
+
+# Optional REPL history
+.node_repl_history
+
+# Output of 'npm pack'
+*.tgz
+
+# Yarn Integrity file
+.yarn-integrity
+
+# parcel-bundler cache
+.parcel-cache
+
+# Next.js (if ever used)
+.next
+out
+
+# Vercel (if ever used)
+.vercel
+
+# Turbo (if ever used)
+.turbo
+