Add test and docs about includes

[rochacbruno]

import os

from dynaconf import Dynaconf

# ISSUE 794
# WHEN USING INCLUDES
# THE INCLUDES ARE LOADED RELATIVE TO
# THE FIRST LOADED FILE `conf/settings.toml`
settings = Dynaconf(
    settings_files=["conf/settings.toml", "conf/.secrets.toml"],
    includes=["**/*.toml"],  # <-- Doesn't start with `conf/`
)

assert settings.a == 3
assert settings.b == 2
assert settings.included_host == "0.0.0.0"

# SO..
# WHEN USING INCLUDES IT IS RECOMMENDED
# TO SET THE ROOT PATH TO THE DIRECTORY
# WHERE THE SCRIPT IS RUNNING
# OR PASS AN ABSOLUTE PATH TO THE root_path or includes

HERE = os.path.dirname(os.path.abspath(__file__))
settings_with_root_path = Dynaconf(
    root_path=HERE,
    settings_files=["conf/settings.toml", "conf/.secrets.toml"],
    includes=["conf/**/*.toml"],
)

assert settings_with_root_path.a == 3
assert settings_with_root_path.b == 2
assert settings_with_root_path.included_host == "0.0.0.0"

closes #794

[github-actions]

Test Results (Python 3.10)

363 tests  ±0   363 ✔️ ±0   34s ⏱️ +2s
    1 suites ±0       0 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit a928113. ± Comparison against base commit eae0773.

♻️ This comment has been updated with latest results.

[github-actions]

Test Results (Python 3.8)

363 tests  ±0   363 ✔️ ±0   31s ⏱️ ±0s
    1 suites ±0       0 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit a928113. ± Comparison against base commit eae0773.

♻️ This comment has been updated with latest results.

[codecov-commenter]

Codecov Report

Merging #796 (3183c69) into master (4ef1614) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #796   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           21        21           
  Lines         1761      1761           
=========================================
  Hits          1761      1761           

Impacted Files	Coverage Δ
dynaconf/base.py	100.00% <100.00%> (ø)

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