docs(event-handler): document catch-all routes

[heitorlessa]

Issue #, if available: #700

Description of changes:

This documents how to use regex for catch-all routes that might be needed in some cases, along with a warning that we recommend explicit routes instead.

from aws_lambda_powertools.event_handler.api_gateway import ApiGatewayResolver

app = ApiGatewayResolver()

@app.get(".+")
def catch_any_route_after_any():
    return {"path_received": app.current_event.path}

def lambda_handler(event, context):
    return app.resolve(event, context)

Checklist

• Meet tenets criteria
• Update tests
• Update docs
• PR title follows conventional commit semantics

Breaking change checklist

RFC issue #:

• Migration process documented
• Implement warnings (if it can live side by side)

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

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View rendered docs/core/event_handler/api_gateway.md

[codecov-commenter]

Codecov Report

Merging #705 (35cdd91) into develop (cdef9c4) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop     #705   +/-   ##
========================================
  Coverage    99.97%   99.97%           
========================================
  Files          116      116           
  Lines         4846     4866   +20     
  Branches       265      267    +2     
========================================
+ Hits          4845     4865   +20     
  Partials         1        1           

Impacted Files	Coverage Δ
aws_lambda_powertools/event_handler/api_gateway.py	100.00% <0.00%> (ø)
...mbda_powertools/utilities/validation/exceptions.py	100.00% <0.00%> (ø)
...ools/utilities/idempotency/persistence/dynamodb.py	100.00% <0.00%> (ø)
...ities/data_classes/api_gateway_authorizer_event.py	100.00% <0.00%> (ø)

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