fix: add _WindowContext class for use in explain operations

[hrodmn]

resolves #68

[github-actions]

Benchmark Comparison

Test	Baseline (ms)	PR (ms)	Change
test_band_access_pattern[multi_band]	1360.3	1337.6	-1.7%
test_band_access_pattern[single_band]	1226.8	1247.3	+1.7%
test_full_compute	621.8	644.0	+3.6%
test_mosaic_method[first]	611.5	635.2	+3.9%
test_mosaic_method[median]	671.8	652.6	-2.9%
test_native_crs_resolution	10794.4	11552.9	+7.0%
test_open_overhead	270.9	277.5	+2.4%
test_reproject_workers[1]	2534.7	2532.0	-0.1%
test_reproject_workers[4]	1345.0	1334.9	-0.8%
test_time_step_parallelism[dask_time_1]	1333.6	1354.7	+1.6%
test_time_step_parallelism[no_dask]	897.0	896.1	-0.1%