Update project description in README.md

[marcuswu]

Added information about fallback to numeric solving using Gonum optimize package.

[github-actions]

⬇️ Go test coverage decreased from 84.7% to 84.7% compared to db7ed92

⚠️ 3 of 12 packages have zero coverage.

• github.com/marcuswu/dlineate/examples/modifiedCylinder
• github.com/marcuswu/dlineate/examples/pentagon
• github.com/marcuswu/dlineate/examples/square

View full coverage report

Updated Package Coverages:

# Package Name                                |  Prior |    New
- github.com/marcuswu/dlineate/internal/graph |  86.2% |  86.1%

View coverage for all packages

# Package Name                                           | Coverage
+ github.com/marcuswu/dlineate                           |    91.4%
- github.com/marcuswu/dlineate/examples/modifiedCylinder |     0.0%
- github.com/marcuswu/dlineate/examples/pentagon         |     0.0%
- github.com/marcuswu/dlineate/examples/square           |     0.0%
+ github.com/marcuswu/dlineate/internal/accessors        |    89.9%
+ github.com/marcuswu/dlineate/internal/constraint       |    96.3%
+ github.com/marcuswu/dlineate/internal/element          |    93.4%
+ github.com/marcuswu/dlineate/internal/graph            |    86.1%
+ github.com/marcuswu/dlineate/internal/numeric          |    75.2%
+ github.com/marcuswu/dlineate/internal/solver           |    94.6%
+ github.com/marcuswu/dlineate/internal/utils            |   100.0%
+ github.com/marcuswu/dlineate/utils                     |    75.3%