Add type annotations #6

Job	Run time
opentelemetry-api	43s
opentelemetry-sdk	50s
opentelemetry-semantic-conventions	38s
opentelemetry-proto	7m 23s
opentelemetry-exporter-opencensus	44s
opentelemetry-exporter-otlp-combined	47s
opentelemetry-exporter-otlp-proto-common	56s
opentelemetry-exporter-otlp-proto-grpc	56s
opentelemetry-exporter-otlp-proto-http	48s
opentelemetry-exporter-zipkin-combined	39s
opentelemetry-exporter-prometheus	46s
opentelemetry-exporter-zipkin-json	41s
opentelemetry-exporter-zipkin-proto-http	49s
opentelemetry-getting-started	7m 17s
opentelemetry-opencensus-shim	3m 17s
opentelemetry-opentracing-shim	42s
opentelemetry-propagator-b3	49s
opentelemetry-propagator-jaeger	46s
opentelemetry-test-utils	42s
	30m 13s

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