Add interface for string element queries based on attributes

[NateLanza]

Does this PR close any open issues?

Closes #17

Give a longer description of what this PR addresses and why it's needed

In Element View:

• Changes the top-level header 'Element Queries' to 'Bookmarked Queries'
• Adds a new 'Element Queries' section containing a form with 3 fields:
  • Attribute Name (dropdown), to select the attribute being queried for
  • Query Type (dropdown), allowing selection between equals, contains, length equals, regex, less than, and greater than.
  • Query (string input), for the query string to match the attribute with based on the type
• Implements element queries similarly to backselection; they cause selection bars in the plot, filter the Query Result table, and show up as bookmarkable under Bookmarked Queries

Pictures/videos of the behavior before and after these changes

No before (the interface shown simply didn't exist)
After:

Have you added or updated relevant tests?

• Yes
• No changes are needed

Have you added or updated relevant documentation?

• Yes
• No changes are needed
• Where is this?

[netlify]

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