feat: pathFilter option [BREAKING CHANGE]

[chimurai]

Description

Removes old "context" , add it back as option.pathFilter (matching functionality did not change)

Before:

createProxyMiddleware('/api', { target: 'http://www.example.org' });

After:

createProxyMiddleware({
  pathFilter: '/api',
  target: 'http://www.example.org',
});

Motivation and Context

• simplify internal code
• simplify public api

How has this been tested?

• CI

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[coveralls]

Coverage decreased (-0.03%) to 98.795% when pulling 12ba812 on path-filter-option into 1540dac on v3.