Add a tooltip for the `Code` field in issues to display the description corresponding to an warning code

[0xedward]

Description:

We want a tooltip to display the description corresponding to the warning code when the user hovers over the warning code of an issue

To implement this feature you will likely need to:

1. Query the warning_messages table to find the corresponding warning code. You can use the get_warning_message_range function in queries.py as a reference on how to write your own query with SQLAlchemy.
2. Replace the following line in Issue.js with HumanReadable and pass in the description we queried for in step 1
3. Make sure you handle the case where the warning_messages table is empty or we don't find a description for the warning code

Steps to Reproduce:

1. Download test-pysa-run.zip
2. Extract the zip file and run the following command to ingest the Pysa test run results into SAPP

   python3 -m sapp.cli analyze taint-output.json

3. Ingest Pysa's warning codes into SAPP:

   python3 -m sapp.cli update warning-codes taint-metadata.json

4. Run the web server

   python3 -m sapp.cli server --debug

5. Visit http://localhost:3000

Submitting a PR

We use the following linters internally, so to save everyone's time, please make sure you run the following linters locally and fix errors related to the files you modified before submitting a PR:

black && usort format . && flake8

To install the linters, you can run the following command:

pip install flake8 usort black==21.4b2