webassemblyhub.io should not allow email-formatted usernames

[jameshbarton]

Describe the bug

1. webassemblyhub.io provided me with an invalid email-formatted username as the default in its signup form.
2. That default username caused my initial wasme build operation to fail.

To Reproduce

1. When creating an account at https://webassemblyhub.io , on the signup form I was presented with a username and email that matched by work email address. I accepted those defaults and my account was established with an email-formatted username.
2. Working through the Getting Started guide, my wasm build action failed with an Error: invalid reference format error. Establishing a different account with a non-email-formatted username succeeded.

% wasme build assemblyscript -t webassemblyhub.io/[email protected]/add-header:v0.1 .
Building with npm...skipping login
running npm install && npm run asbuild
npm WARN workspace No description
npm WARN workspace No repository field.
npm WARN workspace No license field.

audited 5 packages in 0.467s

1 package is looking for funding
  run `npm fund` for details

found 0 vulnerabilities


> @ asbuild /src/workspace
> npm run asbuild:untouched && npm run asbuild:optimized


> @ asbuild:untouched /src/workspace
> asc assembly/index.ts -b build/untouched.wasm --use abort=abort_proc_exit -t build/untouched.wat --validate --sourceMap --debug


> @ asbuild:optimized /src/workspace
> asc assembly/index.ts -b build/optimized.wasm --use abort=abort_proc_exit -t build/optimized.wat --validate --sourceMap --optimize

INFO[0009] adding image to cache...                      filter file=/tmp/wasme372924219/filter.wasm tag="webassemblyhub.io/[email protected]/add-header:v0.1"
Error: invalid reference format
Usage:
  wasme build assemblyscript SOURCE_DIRECTORY [-b <bazel target>] -t <name:tag> [flags]

Flags:
  -e, --email string      Email for logging in to NPM before running npm install. Optional
  -h, --help              help for assemblyscript
  -p, --password string   Password for logging in to NPM before running npm install. Optional
  -u, --username string   Username for logging in to NPM before running npm install. Optional

Global Flags:
  -c, --config string    The path to the filter configuration file for the image. If not specified, defaults to <SOURCE_DIRECTOR>/runtime-config.json. This file must be present in order to build the image.
  -i, --image string     Name of the docker image containing the Bazel run instructions. Modify to run a custom builder image (default "quay.io/solo-io/ee-builder:0.0.32")
      --store string     Set the path to the local storage directory for wasm images. Defaults to $HOME/.wasme/store
  -t, --tag string       The image ref with which to tag this image. Specified in the format <name:tag>. Required
      --tmp-dir string   Directory for storing temporary files during build. Defaults to /tmp on OSx and Linux. If unset, temporary files will be removed after build
  -v, --verbose          verbose output

Expected behavior

1. An invalid email-formatted username should not have been the default choice.
2. An invalid email-formatted username should not have been accepted to create the account.

[Sodman]

Related to (although not a duplicate of) - #137 - These two should probably be tackled together.