Temporary workaround for QKeras installation

[vloncar]

Description

Temporary workaround for installing without QKeras dependency since PyPI won't allow us to submit a package with direct dependencies. Relying on published version of QKeras breaks things, so there's no nice solution.

The workaround is to install qkeras if it is not already present in the environment prior to initialization of hls4ml package itself. It has been tested in various environment configurations and seems to work without breaking other stuff.

Dumbest PR so far!

Type of change

• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Tests

Any import of hls4ml should trigger this.

Checklist

• I have read the guidelines for contributing.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• I have installed and run pre-commit on the files I edited or added.
• I have added tests that prove my fix is effective or that my feature works.