Adding Beeceptor's service virtaulization

[ankitjaininfo]

Type of change

• Add an entry to an existing category.
• Other fixes or amendments.

Rationale

• Adding Beeceptor, an service virtualization platform.
• Sorted the existing Testing list, alphabetically. one entry was out of order.

Checklist

• The contribution follows the CONTRIBUTING.md document guidelines.

Regarding the suggested entry:

• It is sorted alphabetically in its section.
• It does not exist already in the list.
• It is not for marketing purposes.