add minimal documentation for expression filters (#11045)
add minimal documentation for expression filters (#11045)

* add minimal documentation for expression filters

* Update docs/querying/filters.md

Co-authored-by: Clint Wylie <75fd5558bebabcbc02d40b7340cd4722c7741b7e@gmail.com>

* Update docs/querying/filters.md

Co-authored-by: sthetland <6659f19b1818836e086b3a75a303f7d7b7d2b5e1@imply.io>

* Update docs/querying/filters.md

Co-authored-by: Alejandro Lujan <92488b96af66213926f5f4a4428511515b4aa0d3@gmail.com>

* Update docs/querying/filters.md

Co-authored-by: Alejandro Lujan <92488b96af66213926f5f4a4428511515b4aa0d3@gmail.com>

Co-authored-by: Clint Wylie <75fd5558bebabcbc02d40b7340cd4722c7741b7e@gmail.com>
Co-authored-by: sthetland <6659f19b1818836e086b3a75a303f7d7b7d2b5e1@imply.io>
Co-authored-by: Alejandro Lujan <92488b96af66213926f5f4a4428511515b4aa0d3@gmail.com>
mghosh4/druid,mghosh4/druid,nishantmonu51/druid,druid-io/druid,nishantmonu51/druid,nishantmonu51/druid,monetate/druid,monetate/druid,monetate/druid,nishantmonu51/druid,druid-io/druid,monetate/druid,monetate/druid,druid-io/druid,mghosh4/druid,monetate/druid,mghosh4/druid,druid-io/druid,nishantmonu51/druid,mghosh4/druid,mghosh4/druid,nishantmonu51/druid,druid-io/druid,mghosh4/druid,monetate/druid,nishantmonu51/druid