[nr-k8s-otel-collector] add documentation for user's personal collect…

…or config (#1432)

<!--
Thank you for contributing to New Relic's Helm charts. Before you submit
this PR we'd like to
make sure you are aware of our technical requirements:

*
https://github.com/newrelic-experimental/helm-charts/blob/master/CONTRIBUTING.md#technical-requirements

For a quick overview across what we will look at reviewing your PR,
please read
our review guidelines:

*
https://github.com/newrelic-experimental/helm-charts/blob/master/REVIEW_GUIDELINES.md

Following our best practices right from the start will accelerate the
review process and
help get your PR merged quicker.

When updates to your PR are requested, please add new commits and do not
squash the
history. This will make it easier to identify new changes. The PR will
be squashed
anyways when it is merged. Thanks.

For fast feedback, please @-mention maintainers that are listed in the
Chart.yaml file.

Please make sure you test your changes before you push them. Once
pushed, a Github Action
will run across your changes and do some initial checks and linting.
These checks run
very quickly. Please check the results. We would like these checks to
pass before we
even continue reviewing your changes.
-->
#### Is this a new chart

#### What this PR does / why we need it:

#### Which issue this PR fixes
*(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)`
format, will close that issue when PR gets merged)*
  - fixes #

#### Special notes for your reviewer:

#### Checklist
[Place an '[x]' (no spaces) in all applicable fields. Please remove
unrelated fields.]
- [x] Chart Version bumped
- [x] Variables are documented in the README.md
- [x] Title of the PR starts with chart name (e.g. `[mychartname]`)

---------

Co-authored-by: Daniel Budziwojski <[email protected]>

charts/nr-k8s-otel-collector/Chart.yaml

@@ -17,7 +17,7 @@ type: application
 # This is the chart version. This version number should be incremented each time you make changes
 # to the chart and its templates, including the app version.
 # Versions are expected to follow Semantic Versioning (https://semver.org/)
-version: 0.7.2
+version: 0.7.3
 
 dependencies:
   - name: common-library