Added support for SearXNG as a websearch source (#805)
* Created searchSearxng.ts for querying and parsing searxng instance.
Added searxng to the searchWeb.ts to ensure inclusion in the search initialisation script.
Added searxng to +layout.server.ts to ensure the search button is enabled if url provided in .env.local assignment
Updated .env to include searxng configuration
Updated README.md under Web Search Config to mention addition of searxng URL use in .env
* Changes requested
consolidated env variable to SEARXNG_QUERY_URL (felt considering the content the word QUERY was more relevant)
refactored the searchSearxng.ts to generate the query with the new variable
updated related references to variable (.env, searchWeb.ts and +layout.server.ts)
Updated readme and variable comment on .env to reflect the same
* urefectored to display SearXNG in search dialoge when used.
* lint
* types
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Co-authored-by: Nathan Sarrazin <sarrazin.nathan@gmail.com>
