[AIRFLOW-4235] home page dags table: highlight rows on mouse hover

[nandoquintana]

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Jira

• My PR addresses the following Airflow Jira issues and references them in the PR title. For example, "[AIRFLOW-XXX] My Airflow PR"
  • https://issues.apache.org/jira/browse/AIRFLOW-4235
  • In case you are fixing a typo in the documentation you can prepend your commit with [AIRFLOW-XXX], code changes always need a Jira issue.
  • In case you are proposing a fundamental code change, you need to create an Airflow Improvement Proposal (AIP).
  • In case you are adding a dependency, check if the license complies with the ASF 3rd Party License Policy.

Description

• Here are some details about my PR, including screenshots of any UI changes:

In wide screens, home page dags table becomes too wide. There is too much distance between "DAG" and "Links" columns and it is difficult to appreciate which is the icon you should click.

It would be very useful to highlight row on mouse hover.

This could be fixed very quickly, adding 'table-hover' css class to table#dags.

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:

Commits

• My commits all reference Jira issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters (not including Jira issue reference)
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

Documentation

• In case of new functionality, my PR adds documentation that describes how to use it.
  • All the public functions and the classes in the PR contain docstrings that explain what it does
  • If you implement backwards incompatible changes, please leave a note in the Updating.md so we can assign it to a appropriate release

Code Quality

• Passes flake8

[Fokko]

Love it

[codecov-io]

Codecov Report

Merging #5033 into master will increase coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #5033      +/-   ##
==========================================
+ Coverage   76.23%   76.23%   +<.01%     
==========================================
  Files         466      466              
  Lines       30098    30101       +3     
==========================================
+ Hits        22946    22949       +3     
  Misses       7152     7152

Impacted Files	Coverage Δ
airflow/www/forms.py	100% <0%> (ø)	⬆️

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