Add tooltip w/ visx customization to volcano plots

[jernestmyers]

Resolves #66

This PR imports our changes to the @visx/xychart in place of airbnb/visx's latest version. I did so as follows:

• I forked the airbnb/visx repo, made the changes we needed to achieve the desired tooltip behavior, then opened a PR in airbnb/visx
• I branched off my visx fork's xychart-issue-979-tooltip-bug branch to create the deploy-visx-xychart branch where I introduced the gh-pages dev dependency and a simple deploy script
• I built the visx code locally, referencing their monorepo's root package.json scripts
• I ran the deploy script on the deploy-visx-xychart branch (from the visx/xy-chart directory, not the root of the monorepo), which created a new branch with only the visx/xychart package.
• In this PR, I amended the components package.json to import the visx/xychart package from my fork, like:

  "@visx/xychart": "https://github.com/jernestmyers/visx.git#visx-xychart",

Testing

This work can be tested in our normal workflow, by:

1. Checking out this branch (66-volcano-plot-tooltips)
2. Running yarn at the root of the monorepo
3. Spinning up a local mbio-site dev server (and skipping the cache just to be safe) via:

  yarn nx start @veupathdb/mbio-site --skip-nx-cache

[jernestmyers]

NOTE: I'm just glancing back over this and can't see why this would be necessary. Perhaps I'm misremembering something. If not, I'll remove when I address feedback!

UPDATE: Seems to be necessary, one way or another, to set font-weight: normal. Otherwise, all the content is bold. Will keep it as it is.

[jernestmyers]

Here's a screencast demonstrating the styles and the logic that combines pointIDs into a single tooltip when the coordinates are shared.

Note how the grey background uses black text whereas the other background colors use white text. This is to achieve an acceptable color ratio. We may want to render the background colors at the default opacity, which may be more reflective of the marker color as I'm unsure how many users will adjust the marker opacity anyway. Doing so may also necessitate changes to the text colors.

Screen.Recording.2023-08-09.at.12.12.40.PM.mov

[dmfalke]

Regarding building our code with your changes to visx, here is an idea:

In your fork, set up a workflow that builds the code and commits it to a branch named something like dist. In our repo, we can specify your fork and the branch for the visx package. See https://yarnpkg.com/cli/add.

I'm not sure if we will have to do this for all visx packages.

I'll try to find an example workflow that does what I suggested.

[jernestmyers]

NOTE: the directions for testing have been edited. We no longer need to do anything special to test this now that I've deployed the visx/xychart code into a branch on my fork and pointed our components package.json to that branch.

[dmfalke]

I think this looks great!