Settings and initial contents for Bengali localization

[mitul3737]

This PR is to initiate Bengali localization based on

• Issue to Initiate Bengali Localization Team  #339
• https://github.com/cncf/glossary/blob/main/LOCALIZATION.md guide

Base and target branch of this PR is dev-bn which is development branch for Bengali localization.

This PR includes

• [languages.bn] section in config.toml
• content/bn/ directory
• i18n/bn.toml
• Some translated documents
  • Main page
    • content/bn/_index.md
  • Terms
    • "Cloud Native Technology": content/bn/cloud_native_tech.md
  • Others
    
    • contribute: content/bn/contribute/_index.md (partially localized)
    • style-guide: content/bn/style-guide/_index.md (partially localized)
      

Since Bengali localization team owns content/bn/* only,
this PR will require approvals from upstream owners (maintainers).

Track issue: #410

[seokho-son]

Thank you @mitul3737 ! :)

We are going to check following tasks. (target branch is dev-bn)

• 3-1. Adding a new language setting to site configuration https://github.com/cncf/glossary/blob/main/LOCALIZATION.md#3-1-adding-a-new-language-setting-to-site-configuration
• 3-2. Adding a file for site strings https://github.com/cncf/glossary/blob/main/LOCALIZATION.md#3-2-adding-a-file-for-site-strings
• 3-3. Adding a new localization directory https://github.com/cncf/glossary/blob/main/LOCALIZATION.md#3-3-adding-a-new-localization-directory
• 3-4. Minimum required content https://github.com/cncf/glossary/blob/main/LOCALIZATION.md#3-4-minimum-required-content
• 3-5. Check configuration works and open a PR https://github.com/cncf/glossary/blob/main/LOCALIZATION.md#3-5-check-configuration-works-and-open-a-pr

@mitul3737 Could you proceed a build test so that we can check configuration for bn works ? (hugo server)
Please show us a screenshot like #300 (comment)

[mitul3737]

The website works fine now 😁

[mitul3737]

The website looks fine @seokho-son . Can you review it?

[seokho-son]

LGTM :) Thanks!

[CathPag]

LGTM