link parsing should favor on screen urls over offscreen content for huge files

Issue Type: <b>Bug</b> 1. git clone https://github.com/tobie/specref 2. Open the repository in VSC 3. open refs/wg21.json 4. use find to jump to a line, e.g. for `swappability` (on line 121544) 5. try to command click the link on the next line actual results: it takes a really long time before the link is clickable presumption: I'm guessing that the syntax highlighter is trying to parse and highlight all of the lines leading up to the current line. expected results: if the file is large (>10k lines?), skip trying to parse the entire file, and instead try to parse a window around the displayed portion first and then in the background parse the rest of the file. VS Code version: Code 1.55.2 (3c4e3df9e89829dce27b7b5c24508306b151f30d, 2021-04-13T09:36:32.643Z) OS version: Darwin x64 19.6.0 <details> <summary>System Info</summary> |Item|Value| |---|---| |CPUs|Intel(R) Core(TM) i7-4870HQ CPU @ 2.50GHz (8 x 2500)| |GPU Status|2d_canvas: enabled<br>gpu_compositing: enabled<br>metal: disabled_off<br>multiple_raster_threads: enabled_on<br>oop_rasterization: enabled<br>opengl: enabled_on<br>protected_video_decode: unavailable_off<br>rasterization: enabled<br>skia_renderer: disabled_off_ok<br>video_decode: enabled<br>webgl: enabled<br>webgl2: enabled| |Load (avg)|2, 3, 3| |Memory (System)|16.00GB (0.08GB free)| |Process Argv|-psn_0_319566 --crash-reporter-id 1fc67ee2-0174-4598-9f98-4537df0dd32c| |Screen Reader|no| |VM|0%| </details><details><summary>Extensions (32)</summary> Extension|Author (truncated)|Version ---|---|--- open-in-macdown|Cod|1.0.0 vscode-zonefile|Com|0.0.4 vscode-markdownlint|Dav|0.40.4 vscode-eslint|dba|2.1.20 EditorConfig|Edi|0.16.4 prettier-vscode|esb|6.3.2 go|gol|0.24.2 hive-sql|jos|0.0.4 vscode-sbt-scala|lig|0.2.4 hg|mrc|1.7.1 vscode-docker|ms-|1.12.1 vscode-kubernetes-tools|ms-|1.3.0 vscode-postgresql|ms-|0.3.0 python|ms-|2021.4.765268190 jupyter|ms-|2021.5.745244803 cpptools|ms-|1.3.1 vscode-typescript-tslint-plugin|ms-|1.3.3 fabric8-analytics|red|0.3.2…