[Feature] Allow JIRA projects starting with number

[Semprosx]

Is your feature request related to a problem? Please describe.
My organization uses JIRA projects that always start with a number (project code). The regex used by the plugin to determine what is a valid JIRA issue assumes the first character is always alphabetical.

Describe the solution you'd like
Could the regex be adjusted to allow JIRA projects to start with a numerical?

Describe alternatives you've considered
I changed the regex locally on the plugin version used by my organization, and so far I have not encountered issues.

Additional context
None