Add Cloudflare Worker for serving tiles from PMTiles archives in R2

cloudflare/.gitignore

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+dist
+node_modules

cloudflare/LICENSE

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+Copyright 2021 Protomaps LLC
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+3. Neither the name of the copyright holder nor the names of its contributors
+   may be used to endorse or promote products derived from this software without
+   specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+

cloudflare/README.md

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+This is the code for the [Cloudflare Worker](https://developers.cloudflare.com/workers/) that serves tile requests at tiles.openstreetmap.us. The tile data is uploaded as a PMTiles file to a [Cloudflare R2](https://developers.cloudflare.com/r2/) bucket. The worker's job is to handle HTTP requests for tiles by Z/X/Y ID, retrieve the data for that tile from the PMTiles archive, and return it to the client. It also serves TileJSON to describe each tileset, and enforces per-IP and per-Origin rate limits.
+
+The worker code is adapted from [example code in from the PMTiles project](https://github.com/protomaps/PMTiles/tree/main/serverless/cloudflare). See the LICENSE file for details.
+
+## Deploying
+
+To deploy this code, run `npm run deploy`. This uses Cloudflare's "Wrangler" CLI tool to build and upload the code. You can also use the Wrangler CLI to test the worker locally.