Improve scancode license_db

[alok1304]

Improve search

• Search should never filter the Links column scancode-licensedb#48
• Search should only search for license key or license name scancode-licensedb#16
• Update stats wording after the search scancode-licensedb#17

1. Update stats wording after the search.
2. Search box only searches for the license key or license name.
   I use the column-specific search API provided by DataTables. (source: https://datatables.net/reference/api/search())

Reference: aboutcode-org/scancode-licensedb#58

Make table header sticky

Reference: aboutcode-org/scancode-licensedb#63

Tasks

• Reviewed contribution guidelines
• PR is descriptively titled 📑 and links the original issue above 🔗
• Tests pass -- look for a green checkbox ✔️ a few minutes after opening your PR
  Run tests locally to check for errors.
• Commits are in uniquely-named feature branch and has no merge conflicts 📁
• Updated documentation pages (if applicable)
• Updated CHANGELOG.rst (if applicable)

Signed-off-by: Alok Kumar [email protected]