documentation added on FLINT Performance.

[SanjaySinghRajpoot]

Pull Request Template

Description

documentation added on FLINT Performance.

Fixes #77

Type of change

• [x] This change requires a documentation update

[SanjaySinghRajpoot]

@HarshCasper

• The FLINT performance page is here
• The same path was mentioned in issue template #77

Thank You