Tqdm

- add `contrib.slack` (1313)

- `rich`: expose `options` kwargs (1282)
- `autonotebook`: re-enable VSCode (1309)
- misc docs typos (1301, 1299)
- update dev dependencies (1311)

- fix stderr/stdout missing `flush()` (1248 <- 1177)
- misc speed improvements/optimisations

- add `__reversed__()`
- add efficient `__contains__()`
- improve CLI startup time (replace `pkg_resources` => `importlib`)
- `tqdm.autonotebook` warning & `std` fallback on missing `ipywidgets` (1218 <- 1082, 1217)
- warn on positional CLI arguments
- misc build/test framework updates
+ enable `py3.10` tests
+ add `conda` dependencies
+ update pre-commit hooks
+ fix `pytest` config (`nbval`, `asyncio`)
+ fix dependencies & tests
+ fix site deployment

- fix minor typo (1246)
- minor example fix (1246)
- misc tidying & refactoring
- misc build/dev framework updates
+ update dependencies
+ update linters
+ update docs deployment branches
- misc test/ci updates
+ test forks
+ tidy OS & Python version tests
+ bump primary python version 3.7 => 3.8
+ beta py3.10 testing
+ fix py2.7 tests
+ better timeout handling

- fix notebook memory leak (1216)
- fix `contrib.concurrent` with generators (1233 <- 1231)