Enclose column names in double quotes in filter docs and tests
Suggest enclosing column names in double quotes in filter docs for robustness with non-alphanumeric characters.

Note that the viewer uses DuckDB: https://duckdb.org/docs/sql/introduction
> DuckDB’s SQL dialect follows the conventions of the PostgreSQL dialect.

And in PostgreSQL SQL Syntax: https://www.postgresql.org/docs/11/sql-syntax-lexical.html#SQL-SYNTAX-IDENTIFIERS
> Quoted identifiers can contain any character, except the character with code zero. (To include a double quote, write two double quotes.) This allows constructing table or column names that would otherwise not be possible, such as ones containing spaces or ampersands.

Fix #2794.

CC: @lhoestq 
Enclose column names in double quotes in filter docs and tests: Suggest enclosing column names in double quotes in filter docs for robustness with non-alphanumeric characters.

Note that the viewer uses DuckDB: https://duckdb.org/docs/sql/introduction
> DuckDB’s SQL dialect follows the conventions of the PostgreSQL dialect.

And in PostgreSQL SQL Syntax: https://www.postgresql.org/docs/11/sql-syntax-lexical.html#SQL-SYNTAX-IDENTIFIERS
> Quoted identifiers can contain any character, except the character with code zero. (To include a double quote, write two double quotes.) This allows constructing table or column names that would otherwise not be possible, such as ones containing spaces or ampersands.

Fix #2794.

CC: @lhoestq 