v0.5.0: make pre-release changes (#76)

• FEATURE: add support of the $__interval variable in queries. See this issue.
  Thanks to @yincongcyincong for the pull request.

• BUGFIX: correctly pass time range filter when querying variable values. Before, time filter wasn't applied for /field_values and /field_names API calls. See this and this issues.

• BUGFIX: fix the issue with displaying incorrect subfields when requesting logs with different set of fields. See this issue.

v0.4.0

• FEATURE: make retry attempt for datasource requests if returned error is a temporary network error. See this issue

• BUGFIX: fix dynamic variable issue causing this is undefined error. See this issue.

• BUGFIX: fix multi-value variable handling to properly format queries. See this issue.

• BUGFIX: fix issue with special characters in variable values. See this issue.

v0.3.0

• FEATURE: add beta version of the query builder. The builder allows selecting field names and field value. See this issue.
• FEATURE: add support for loading data for variables, including log field names and values. This feature allows querying /select/logsql/field_names for field names and /select/logsql/field_values for field values. See this issue.

v0.2.6

• BUGFIX: fix issue with forwarding headers from datasource to the backend or proxy.
  It might be helpful if a user wants to use some kind of authentication. See this issue

v0.2.5

• BUGFIX: fix bug with a parsing response when the time field is empty but the message and labels are present.
  It happens when the user tries to show only the stats number. See this issue.

v0.2.4

• BUGFIX: fix bug with parsing response when one of the field contains ANSI escape sequences. See this issue.

v0.2.3

• BUGFIX: fix bug with displaying response when one of the stream field is defined and lines are not collected. See this issue.

v0.2.2

• BUGFIX: fix bug with displaying responses with a custom set of fields. See this issue.
• BUGFIX: change time range limitation from _time in the expression to start and end query args. See this issue.

v0.2.1

• BUGFIX: change the metrics flag from false to true in plugin.json to ensure the plugin appears in the Grafana datasource selection list.

v0.2.0

• FEATURE: add support for variables in the query. See this issue.

• FEATURE: add client-side record limit check for VictoriaLogs < v0.5.0 support. See this issue.

• BUGFIX: fix a bug where a manually removed filter would persist in the query after the "Run query" button is clicked.See this issue.

• BUGFIX: fix query handling to correctly apply _time filter across all queries. See this issue and this issue.

• BUGFIX: fix an issue where sometimes an empty response was returned despite having data in VictoriaLogs. See this issue.