Added helper functions to return current plugin extension, file_type … #1023

Job	Run time
build-ffi	2m 17s
build-coverage	2m 48s
build-cross-targets (aarch64-unknown-linux-gnu)	2m 3s
build (macos-latest, --all-features)	2m 11s
build-cross-targets (armv7-unknown-linux-gnueabihf)	2m 43s
build (macos-latest, --no-default-features)	1m 44s
build-cross-targets (i686-unknown-linux-gnu)	2m 22s
build (ubuntu-latest, --all-features)	1m 20s
build-nostd (macos-latest)	1m 10s
build (ubuntu-latest, --no-default-features)	1m 14s
lint	1m 3s
build-nostd (ubuntu-latest)	38s
build (windows-latest, --all-features)	2m 26s
build-nostd (windows-latest)	1m 37s
build (windows-latest, --no-default-features)	2m 29s
test (macos-latest)	1m 46s
test (ubuntu-latest)	1m 34s
test-cross (aarch64-unknown-linux-gnu)	2m 41s
test (windows-latest)	1m 36s
test-cross (i686-unknown-linux-gnu)	2m 32s
	38m 14s

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