Update environment-variables-section.md

[colinmollenhour]

If the config file is this:

env:
  ENVIRONMENT: x
  INSTANCE_UID: x

# Main Fluent Bit Configuration
service:
  flush: 1
  grace: 0
  daemon: off
  log_level: debug
  parsers_file: parsers.yaml

# Include input configurations
includes:
  - inputs/*.yaml

# Output to stdout for testing
pipeline:
  filters:
    - name: modify
      match: "*"
      add:
        - environment ${ENVIRONMENT}
        - instance_uid ${INSTANCE_UID}

  outputs:
    - name: stdout
      match: "*"

If I run this with docker run -e ENVIRONMENT=dev ... it is still reported as "x"

[esmerel]

Two stylistic changes, otherwise looks good to me.

[esmerel]

Made a couple of minor changes and merging. Thanks @colinmollenhour !