Bump dependencies

[cmdcolin]

The plugin-template kind of has an ongoing battle to ward of stale dependencies

• This PR proposes to update jbrowse v2->v3+react+mui
• Update eslint
• Remove cross-var (gave errors about babel 6)

I am also considering that it might be useful to remove the yarn setup and yarn init requirements. This isn't yet done on this PR but i am considering removing yarn setup and yarn init

This has prevented us from properly running in the CI, and makes it harder for us to test our own usage of the plugin-template (REF: #33)

[cmdcolin]

here are the babel 6 cross-var errors

 y test:e2e
yarn run v1.22.22
$ cross-var start-test "npm-run-all --parallel start browse" "$npm_package_config_port|$npm_package_config_browse_port" "npm-run-all cypress:run"
/home/cdiesh/src/jbrowse-plugin-template/node_modules/babel-core/lib/transformation/file/options/option-manager.js:328
        throw e;
        ^

Error: Requires Babel "^7.0.0-0", but was loaded with "6.26.3". If you are sure you have a compatible version of @babel/core, it is likely that something in your build process is loading the wrong version. Inspect the stack trace of this error to look for the first entry that doesn't mention "@babel/core" or "babel-core" to see what is calling Babel. (While processing preset: "/home/cdiesh/src/jbrowse-plugin-template/node_modules/@babel/preset-react/lib/index.js") (While processing preset: "/home/cdiesh/src/jbrowse-plugin-template/node_modules/babel-preset-es2015/lib/index.js")

instead of using cross-var, we just hardcode some values. it is a relatively small number of places where port number is used, and so i think it is ok

the plugin name is not consistently applied anyways from package.json cross-var config variable section, so i think it is also ok to remove